Radiologists mostly have nothing to do with pharmacologic treatments. The only drugs they need to know (at most) are analgesics, sedatives, local and regional anesthetics, a few opioids, basic antibiotics, basic antiallergics, drugs of coagulation and thrombolysis, and ACLS meds. They don't rountinely prescribe outpatients meds. Not too many ophtho, ENT, neurosurg, urologist, psychiatrists, pathologists know much about lipid-lowering drugs either. Lipitor vs. Zocor vs. Ezetimibe vs. niacin vs. cholestyramine is the domain of other specialties. The other day, I called an ophtho guy and said his patient has bilateral DVT. He asked me what the treatment was. I told him to start him on a heparin IV drip and start coumadin and gave him the doses and how to follow them by PTT and INR. He then asked me if he should double the dose of the heparin, since it's "bilateral DVT". Funny, but true. So, you see that most doctors don't know what's outside of their own field. But this is not a shortcoming. If you specialize in something, you can't catch up and will forget the rest of medicine. That's what the other specialties do. Radiologists do other stuff than prescribe lipid-lowering or antihypertensive medications. Ask that pharm rep of yours what gradient echo is or what a hounsfield unit of zero means. Of course he wouldn't know. Everybody knows their own field. Medicine is too broad these days.
Thinking why radiologists don't do what primary care docs do is very naive. And no, radiologists do not carry around stethoscopes and don't fit your "traditional doc image". However, in this day and age, they are at the forefront of medical advancement. With less and less dependence (and knowledge) on physical exam and less tolerance for uncertainty, the role of radiology has become central to modern medicine, especially in recent years. The majority of major medical decisions are made on the basis of radiologic studies in this day and age. The demand for radiological expertise has grown more than demand for any other specialty. A recent study by Merritt Hawkins showed that radiologists are the most in-demand specialty. Ortho and cardiology were a distant second and third.
I don't blame you that you don't know much about radiology. The average medical student knows less about radiology than most other fields of medicine, since they are minimally exposed to it during medical school if at all (Hence, a thread like yours). Even if they are exposed to radiology, it's minimal compared to what they get exposed to in medicine, surgery, peds and when they do, they get minimal exposure to plain films only and none of the more advanced modalities or procedures. Even the surgery resident that you spoke to probably doesn't know anything about radiology.
Do I think I know a lot about medicine? Absolutely. (of course within my own personal limits). Radiologists are without doubt and by far the most knowledgeable of physicians overall, even more than pathologists and internal medicine docs. Any fair physician knows and acknowledges this too (our chief of IM does, and wishes people as bright as radiology residents went to his IM residency). You are required to know almost all the diseases of all organs and interact with almost all specialties, often a formidable task. That's why the radiology boards exams are perhaps the most difficult. You don't have to know much about the treatment of these disease entities, however, unless when radiology plays a central role in the treatment of those diseases (i.e., minimally invasive treatments). You have to do an extremely large amount of reading to become a good radiologist and maintain your competence, since radiology is growing at a more rapid pace than almost any other field. Even radiology itself is getting more and more subspecialized, just because of the fact that there is too much to know and one person can't keep up with the growth in knowledge.
It is true that radiologists have little patient contact. However, it's not as little as you think. When doing ultrasounds, GI and GU fluoro studies, biopsies, FNAs, image-guided injections, and all interventional studies, they have some patient contact. Many of them are quite happy with this small patient contact that they have, since it doesn't involve a lot of what they consider boring and BS (e.g. social, drug abuse, nursing home, noncompliance, placement, etc.) that plagues your "traditional" patient contact, esp. in the primary care setting.
The lifestyle issue is also exaggerated. The workload of radiologists has increased dramatically. They now have one of the longest hours. See this thread:
http://forums.studentdoctor.net/showthread.php?threadid=101722 . If you want radiology for it's fewer number of hours, you will be severely disappointed. This, however, was not the case ten years ago and radiologists did not work too hard at all. That stereotype still persists in the outsiders' minds, but it's changing. In big and busy training institutions, the radiology residency call is extremely tough and intense with your multiple beepers going off every 5 minutes throughout the night, though call frequency is not too often. I once had to do q2 call for a block, but that was quite unusual. In my hospital, even a few OB and neurosurgery residents have confessed that we work harder than them when on call. The upside is that our calls are much less frequent (no q3 unit calls). My friends and I who did "hardcore" university hospital IM and general surgery internships have found that our so-called "tough" internships were a joke compared to the intensity of our radiology calls as a PGY-3. Note that in many programs, call doesn't start until the PGY3 year, because before that you are not "even considered qualified to take call", again something to be said about how much you need to learn in radiology residency. Also note that most of radiology call is during the PGY3 and PGY4 years, a time in your career when your colleagues in most fields are getting a much lighter call schedule. It's not so pleasing to become an intern again when you are PGY3. You will have a good lifestyle when not on call or during your PGY2 and PGY5 years. All that said, I'm sure there are less intense radiology programs around as well.
It's very hard to get a sense of what radiology is before you do it. I find it boring just sitting and watching an attending go over a case, even as a radiology resident. I would be even more bored if I were a med student watching, since it would seem like just going back and forth through a bunch of images, without knowing the significance of the findings and without the need to heavily concentrate on every portion of every image trying to make sure you catch all the findings. However, when I'm doing it myself, it is extremely challenging, both intellectually and by knowing the fact that I'm helping patients and doctors alike, even if that patient I helped or saved never sees me in person.