I'm just curious, because I'm tired of seeing all of the first years in anatomy wear their scrubs everywhere (I really hope they're clean when I see them in local stores/car/etc) and tired of seeing second years wear their stethoscopes around their necks and white coats everywhere.
Contrary to popular belief if you have a 30-45 minute car ride to the hospital/Dr's office to shadow (where you will need your white coat) you don't need to wear it while you sit in your last hour of lecture, walk to your car, drive, stop at wawa/gas/dunkin donuts, etc. You can put it on in the parking lot of the place you're going to

. And you can even leave in your car while you're in class all day! (Double

!)
Also if you have a physical exam workshop where you're learning the cardiac exam, you don't need to take your stethoscope out of the box that's in your bookbag and wear it around your neck all during lunch. You won't be using it for over an hour and half later.
Ah, well. It is excessive, but not unexpected. For most, I don't think it's out of frank pretentiousness. I think pre-clinical students are just overzealous and want to show their pride and excitement, as others have mentioned. That's normal, in my opinion. As a kid, did you ever want to be a fireman or something and wear your play fireman gear everywhere? It looks silly, but one can only chuckle in empathy. When most pre-clinical students wear their gear, sometimes in inappropriate places, it is funny. They often look silly to me, like they are wearing play gear.
During my first two years, I was forced to wear scrubs to school, since it was part of my dress code. I didn't like it at first, but then I got used to it. After a while, I got lazy and didn't feel like changing my clothes all the time when I knew I would be going back to the anatomy lab for a long night, or was just too tired after a long day at school, so sometimes I'd go out on errands with my scrubs still on. It was hardly out of pretentiousness, I assure you. And I hated to wear my white coat and I wouldn't unless I was directed to. To me, it was like wearing something that was a couple sizes to large for me. I would need to grow into it.
I haven't experienced third or fourth year yet, please tell me things go up from here?
I can tell you from my perspective. If anything, third year is anything but pretentious. Most will feel more humble than ever. You begin to realize the extent of how much you actually DON'T know and how much you have to learn. You don't quite know how you can fit in on the team, so sometimes you can even feel useless. The pimping and long hours will pretty much humble most people very quickly. When I wear my white coat now, it feels heavy on my shoulders, because of the increased responsibility and I don't like it when patients confuse me all the time for a real doctor and even though I make efforts to correct them, for some reason white coat = doctor, no matter what I say. It makes me feel very uneasy. I don't like to wear my white coat out anywhere, except at work. I never did. However, now, it's more because I use it like a real lab coat. I still wear scrubs everywhere around the hospital because for my current rotation I assist with deliveries and surgeries often. I don't hate my pager, but hearing it go off sometimes brings a pang of fear.
I know that some find third year to be somewhat disparaging. I find third year to be very fun and exciting. This is why I chose medicine years ago and finally I am beginning to get my feet wet. I try to do as much as I can, even though as a medical student in clinical rotations, you can't do much. Sometimes, however, you can actually do something that really helps out the team, or a patient and you feel good. Those times stick out for me much more vividly than the profound lack of sleep and the endless pimping (which actually isn't so bad, because it helps you learn).