The real question is why you're even contemplating being a solo founder. Discounting you actually wanting to be solo (that's a whole different kettle of fish) the reason is probably because it's really hard to find a co-founder. Co-founder dating doesn't work, meetups have terrible SNR, etc.
It's an unfortunate (for the rest of the world, YC might disagree) fact that the best place to find a co-founder are places like Stanford. Elite US universities, which encourage entrepreneurship, where external factors align to create lots of liquidity around able co-founders.
So while I think something like the YC Fellowship is great, the team has missed the boat. The actual problem in very early stage startups is not money, but suitable co-founders.
(Of course I'm totally biased, since I run a startup program based on this concept in the UK [1].)