I gotta say, part of the reason i use Kano is cos nobody else does. Whenever someone else picks Kano online i get all stroppy, ESPECIALLY if they beat me lol. I hate seeing characters overused...but this game isnt nearly as bad as some of the other games in the FGC
I think the reason nobody uses him though is cos, as much as i love him, he just really doesnt have any depth. he doesnt have any real severe disadvantages or anything but he doesnt really excell in any particular area either. There's not gonna be any groundbreaking new discoveries with him that'll make him top tier or anything. I certainly dont think he's a bad character, far from it (there are NO bad characters in this game), but NRS really did spoil some chars rotten by giving them every tool in the shed and not sharing them out with the rest of the cast (Kung Lao im lookin at you). Sometimes i think they picked out the important story goodguy characters and/or the most popular ones that sell the most merchandise or whatever, and went out of their way to make them the best.
I will say, however, (and i've said this since day one) that Kano is by far the most fun character to play (Baraka and Mileena are up there too). That's just a bloody lucky coincidence though, in my case, cos he's been my favorite char since MK1...(until Baraka came along anyway, now i've got 2 favorites. Rich Divizio characters FTW)
I strongly believe that you should pick your main either because a) Its your favorite character and/or b) They are the character you have the most fun using. However, i understand that the pros need to win in order to keep their sponsorships, so you can't really blame them for tier-whoring.