YC companies are, to the best of my knowledge, mostly looking for unicorn-style plays. That's a very different game to a lifestyle business, and one where I would agree 100% that the failure rate is extremely high.
Small business failure rates: well, for starters, the usually-quoted numbers have been updated as of late. A quick Google shows that most sources are converging on around a 60% success rate for small businesses at the moment. (I think that's actually unrealistically high - I'd estimate more like 40% and guess they aren't accurately polling online businesses, but hey.)
Secondly, there's a significant difference between small business failure rates and small businessperson failure rates. As I mentioned above, most people's first businesses will fail. That will obviously skew the numbers in favour of failure: indeed, given that it's surprising the survival rates are as high as they are.
You're correct that it's (sometimes) easier to build a successful business after you've already built one. However, you don't mention the secondary point, which is that it's also much easier to build a successful business after you've already tried really hard and failed at one.