Oh yeah because jeans and a shirt are so fucking uncomfortable.  Your a moron Xant the shit you come out with.
Must be my pure Russian blood talking, but i have to agree with Xant on this one... You can't run or falcon-kick anyone efficiently, while wearing jeans. 
Shirt?... Can't imagine a less comfortable top ( t-shirt, tank-top, sweater, pretty much anything is more comfortable than a shirt ).
If i had to base my cloth preferences exclusively on comfort, i would never leave the safe haven of my grey sweatpants, a lose hoodie with a zipper and  a pair of ASICS running-sneakers. Can't beat the comfort of these three items. 
EDIT:
my perfect set:
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