Why don’t we all monetize our hobbies? Why don’t we market our personal lives? Why don’t we each have our own line of branded merchandise? Why haven’t we written a memoir?
Because some people don’t want to! And that’s okay.
Trying to start a new social network (or whatever you'd call Reddit) from the ground-up is not only very likely to fail, but it's also a totally different skillset than building iOS apps. Of course he'd rather just find another job.
His point was that there is a big difference between building a product and operating a service. I can understanding not wanting to do the latter, because it's a COO job and unless you like doing that it is not fun.