Probably because of arcade stick compatibility, PS3 controllers aren't compatible with the PS4, the same probably apply to sticks and other USB accessories. (cyberfanatix.com)
This might involve providing some gaming gear, like arcade sticks, or running a tournament bracket as part of the event. (ozhadou.net)
There's no question these people are serious; many (or maybe even most) brought their own arcade sticks and everything. (thatvideogameblog.com)