Im currently doing a PHD that I'm using maya to do a lot of things in, possibly not whats it's designed for but it works perfectly to get my theories down before I invest a lot of time in doing the actual work, I'll also be using it to proces and help to analyze the data that I gather.
As for personal reasons I generally model, animate and render for fun, just to see I can push myself to do some really good stuff! I generally dont go for low poly but mainly realism if possible but on my lateest side project I'm having to cut it back a bit as I'll run into loads of problems with a lot of polys!
"No pressure, no diamonds" Thomas Carlyle