There are good reasons to wear any and all of the above under different circumstances, pragmatic reasons.
A formal canvas uniform equalizes everybody into wearing defacto sack cloth with no gender, no differences in fabric, no zippers, no sequins, spangles, what have you. Rich or poor, old or young, male female everybody is equal, period.
You can tear, shread them to your hearts content and they stand up pretty well to "abuse" (except the dryer). There are other things to be worn, street clothes but who wants to rip their best blouse, their suit jacket, rip their shirt to practice day in and day out.
Tees & sweats, money and someones wealth, someones gender might enter into the equasion more prominantly perhaps. Hey he's wearing the $200 sneakers and I've only got the $20 dollar ones.... it can become an issue.
I like the white sack cloth