Different people enjoy different things. For example, many hackers would prefer to work at a company where they could concentrate all their time on coding rather than start a startup themselves where they'd have to spend much of their time doing other tasks.
Reality of start-ups: if you're a founder and spend all your time coding, you're going to fail. I love coding, so I'd have to have an extremely compelling vision were I to do anything else.
If you've got the skills, but no experience with the start up scene, it would be a great time to hone your skills while learning about what it really takes to make a business work (from scratch) first hand. You would come out (more) ready to do it on your own idea on the other end.
But yeah if you've got an idea and the skills and the motivation required, by all means apply you YComb yourself.
If a company goes under the founder may have ended up living frugally as possible for a long period of time for no end reward. The employee has been there with them, faced the same challenging work but has had a comfortable wage the whole time and are just out of a job.
That being said may people would much prefer to take the risk as founder, there are plenty of other people out there though happy with the employee role at a startup for the time being or may have already tried the founder path.
Being an employee is significantly less risk and less stress than being a founder. Most of these companies have funding, traction, and a real product. It's different than being given $17K to make something of yourself, and presumably appeals to different people.