I like the idea of tradition. My grandfather, in retrospect, was/is always appropriately dressed. My father on the other hand has a closet full of tweed jackets and such that he bought back when small independent menswear shops still existed in Canada, but he seems to have fallen out of the habit as workplaces have become more casual. I consequently never learned anything about clothes, so I find it amusing that I am in some sense now recapturing this knowledge, just as I am recapitulating other parts of my grandfather's life (advanced professional training in London, etc—my Uncle told me recently of being in London in the 70s, and being dispatched by his father back on the prairies on to Jermyn St. to get a college tie from T.M. Lewin!).
On that note, most of my relatives are in the same ancient profession, one I didn't choose to join. Instead, I somehow ended up in law, and I think part of that had to do with the clothes, at least insofar as they indicated a defined societal role, and offered a symbolic counterweight to the stethoscope & white coat, etc. (This was obviously not the only reason!) We have barristers' robes where I'm from, so this is more obvious. It also helped that one of my colleges made me wear a gown now and then during term.
It should be said though that I am at the same time aware that a lot of "dressing properly" has to do with class, and it does make me uncomfortable how my sartorial choices are sometimes at odds with my political ones—were someone to say I was a "suit" I might think them a little dim, but I would be reminded that I have, in fact, met the kind of person they mean. While I derive some pleasure from cleaving to historical forms that are for the most part irrelevant today (my "professional" excuses notwithstanding) I acknowledge that it's not really the fault of most people that they buy the reasonably priced clothing on offer at the high street, and that I am engaging in a fundamentally conservative enterprise.
Another reason I dress the way I do, only slightly less problematic, is that as someone who has spent so long in school it makes me feel a bit more "adult." Not that I haven't been for a while, but I think I have always been a bit more serious, a bit more reserved than my peers. The clothes match how I feel, compared to how I see others act—and dress. This is more important when you're in university for the better part of a decade.