They make yoga clothes that can also be worn to work. It's happening, at least in places.

Yeah I'm not sure I'd categorize all the 90s-era Star Trek onesies as "comfort wear"... especially not on characters with male genitalia. Maybe the 24th century characters didn't care, but I always felt second-hand embarrassment for the 20th century actors!

Lovely idea, except that to some?/many? people, tracksuits are possibly the least comfortable clothing ever. Nasty clingy sticky plasticky weak sweaty flimsy things.