Lots of YC applicants these days view YC as the starting step. If they get in, they will "do a startup". If they don't, they won't. They are really more in love with the idea of being part of the startup community than the idea of actually building a company. They're outsiders peering into the walls of Silicon Valley and thinking there's some magical formula for success waiting there for them. Of course, they won't tell YC this.