Hmmm...I think that the students who drew the scientists like regular people were missing the point. If you're going to make a drawing that is identifiable as a "scientist" you should draw him/her in a labcoat. True, they do not wear them all the time, or even most of the time. But, that would make it easy to identify the picture and makes it undenyably a scientist (or a photo technician, pharmascist, doctor)
If somebody asks you to draw an astronaut, do you draw a picture of Neil Armstrong going to the supermarket? Do you draw a picture of John Glenn eating breakfast?
If somebody asks you to draw a picture of a general, do you draw Colin Powel cleaning his garage?
NO! You draw them as they are normally thought of.
Also...I have had a few professors who had a tendency to wear labcoats. One was a chemistry professor who wore it eventhough he was teaching class and not getting his hands dirty in the lab. Also, I had a physics professor who wore one.
I think they wear them because they're hella cool!
I don't think we should say scientists "have to" wear labcoats. We should say they "get to."
I wear a labcoat too sometimes, but I don't have a Phd or a nobel prize or anything, so I'd be a poser if I wore it all the time. Instead, I wear it whenever I had a good excuse to. Such as when handeling volitile chemicals...like putting gas in the lawnmower.
-Steve