I question what reasons someone would have to be unwilling to move to the Bay Area for 3 months given the amount of founders that claim that YC was the tipping point for their companies.
OK, just to give one example... my co-founder is married, and her husband is in graduate school. So either he'd have to interrupt his education to come with her, or he'd have to accept her running off to the opposite side of the country for three months, chasing a dream that he might or might not be fully sold on. We honestly haven't had the discussion yet, but my gut feeling is that this would be a very hard sell. And YC make it clear that they expect all (or at least a majority) of the co-founders to make the trip.
Also, we have a local incubator (Triangle Startup Factory) that is (potentially) an option for us, which would not require any relocation at all.
Given that, it's not exactly a "no brainer" to apply to YC. I'm not saying we won't do it (either now or in a future cycle) but it's not necessarily an easy decision.
Aside from that, though: Who can't live alone for 90 days? Seriously? When Virgin America NYC/SFOs are sub-$200 roundtrip?
Snark apart, some of us have a priority order that places family above work - even good, interesting, start up work. I'd never choose to live apart from my spouse for 90 days.
I'd like to do YC myself, and being single (although not "just out of college") it would be pretty easy for me to do. But my cofounder has a say in this as well, and I have to respect her position.
Anyway, I was just giving one example of a situation where the decision is a bit complicated.
YC probably wouldn't be interested in funding such a startup, and rightly so for them. But there's loads of startups that aren't YC's niche, all of them swept away by your statement I quoted.
YC is not for founders who like to go their own route, who like to figure stuff out on their own, even if it takes more time and is more risky. If you have too much handed to you, you will not learn as much as you would from your mistakes. Also, just based on HN there seems to be an awful lot of groupthink around YC (not the partners I'm sure), which is annoying to lone-wolf types.
Btw. I think your "tipping point" statement has a lot of survivor bias. Was it a tipping point for the ones that ended up going nowhere? Well, not, by definition. And for the ones that did and raised a series A, yes of course it was, but so is raising a series A without YC.