It's an IPO, the P is public. The information needs to be consumable by the public. The level of knowledge that can be expected of a random IPO stock buyer isn't the same as that of a VC or private fund.
And that's exactly where the SEC comes in. The 1930s went wrong enough, no point in doing a 2030s repeat.
Public-stock buyer or IPO buyer? The latter tend to be sophisticated.
I absolutely agree. But it's entirely irrelevant, because there's no "must be this (hand gesture) sophisticated to buy IPO stock" rule.
Legally, no. Practically, all underwriters have account minimums and tenure requirements. The only exception is direct listings.
I'd wager that the 95th percentile, and maybe the 99th percentile anthropic IPO participant, by volume, is a more sophisticated stock evaluator than either you or me.