I find that in video games it is decidedly harder to simply tell a large group of people to go out of their way to do something. If someone types in the chat "GO VOTEKICK THIS GUY" chances are people are going to ask why, whereas if they get a big message saying "type /yes to forget this guy over" they would be much more likely to do it.
It's a small technicality, but you can understand what I'm saying right? If someone's telling you to do something rather than just giving you the option, you're less likely to do it. Everyone has to go take an initiative to get someone kicked, and in this system there has to be a tally instead of a /yes /no percentage.