How could it not be luck of the draw? Do you understand how rare IPOs are?
> Why have none of the ~940 YC companies ever gone public via IPO?
I take issue with your implication: "YC has had no IPOs after funding ~1000 companies". That is a premature call, and (frankly) bending the truth. YC has been taking on more startups per year recently. That skews the age of YC companies to very young. If you assume that an IPO takes > 5-6 years, then results for the vast majority of YC companies aren't even in yet.
> After 10 years of success, and a lot of VC-backed companies that would be looking for eventual exits, that seemed like a surprising statistic.
Sure, YC may have fewer IPOs than normal VCs. That's because they are an early-stage investor, which has much higher risk. Thus, you would expect fewer IPOs compared to a late-stage investor.
> is it something special about the YC ecosystem that tends to not culminate in an IPO,
Citation needed. What is the "expected" number of IPOs? Are there similar early-stage VCs that have more IPOs?
It sounds like you are trying to dig for a problem that doesn't exist.
It's like complaining that your favorite baseball team hasn't had enough no-hitters. Who cares, as long as they are winning!