y'all are harsh and mean.
i've written LOR's when i was a TA and then as mentor and tutor since. just remember that the prof is a person, too. with a job and work to do and a family and hobbies, etc., and probably a gazillion people ask for med school LOR's every year. so, that in and of itself could create some bitterness towards the whole process, since writing these letters is not a paid part of the job, nor something that helps them at all (as opposed to writing an LOR for someone going to grad school in their field, which has the benefit of having them get to sell a student to a colleague, populate their field with someone with some of their indoctrination, etc.), and there are likely a lot of them to do. this is said if the prof is NOT a research mentor, mind you, since research mentors take on those kinds of trappings when they take you as a student. secondly, MOST people do what they do because they love it and think it's the best thing in the world and can't understand why anyone would rather do something else. you probably think that about medicine, yes? not everyone in the sciences, nay, very few, "end up" professors by default. it's a long hard road of it's own, with many fewer outward benefits than law or medicine, etc. so love of the work, and teaching, is key. so, in this way, if you think from their point of view, if they think that you are either only interested in their class, or their research lab, because you want AMCAS fodder and a good med school LOR, how they could feel used. no one likes feeling used. and even if you actually have a passion for, say, p-chem class or that blot work, i guarantee hordes before you have conditioned that prof to be wary of the pre-med.
mentors and teachers put in a lot of work, and care a lot (for the most part). if they think you see their passion and effort as merely your vehicle for something removed, it hurts.
there is also the fact that many actual doctors aren't all that, and everyone has had a bad doctor or two, and if you're older you prolly know what i mean. these profs have had, at some point, to deal with an ill or dying relative, or illness themselves, and have at some point encountered an awful doctor who's either been haughty or unsympathethic, or worse, incompetent. if you've worked with them and they respect and like you, they might want you in their field instead of in a field that they see as hit or miss in terms of quality.
now, my old prof's have been great for me in this process. my undergrad advisor and my grad advisor, who are now colleagues, are being very supportive of me because of our relationships. but my boss keeps asking me if i really want to do this med school thing, how much better what we do is, how more globally important, how much more it takes etc. and in some ways, he's right. but medicine is my calling, i can feel it, and i believe in mdeicine, but i still had a hard time talking him into writing a good rec...
