Wow. I haven't looked at any of your other posts, but I hope you didn't put your foot in your mouth before writing them like you have with this one.
I can give you a great example of a successful nurse who went on to become a doctor (and is also still a nurse BTW). I can give you an example of a successful PA who went on to become a doctor. Being a physician, one probably holds the most responsibility in his/her job (not true with all docs, but most in the health field), so I can see why so many aspire to become physicians.
But - and try and wrap your brain around this now - some ACTUALLY decide they would like to be a nurse or PA because they are interested in it and don't really WANT to be a doctor and have to deal with med school and being on-call and so on, and do just as well in the pre-reqs as pre-meds. I know, I know, hard to believe, right? (sarcasm here)
Sure, some would not have cut it in med school, and some find out IN med school that they can't cut it. Unfortunately you don't really have the data to back up your statement of a pre-nursing student not being able to cut it in med school.
Oh, and DO = MD (at least in the real world), get it? Good.