I think going public early is better. VC’s and insiders have been capturing the lion’s share of early-stage growth returns. If companies go public earlier, more of that growth will be accessible to more investors.
A truly open market strips away a lot of the advantage insiders and old money have enjoyed for a long time, and keeping growth companies in the private market is a way to prolong that privilege.
I'm inclined to agree with you that defending some sort of insider advantage is part of the reason, along with expensive regulations and avoiding manipulative, activist speculative behavior.
(Yes, for real, I have one)
Uber was losing between $1B and $5B a quarter when they IPO'd. In the last quarter of 2020, Uber lost close to $1B, and they're still valued at $108B, with no real long term plan for survivability. The way I see it, risks include legislative changes WRT driver status, bad press, self driving cars, a post pandemic world where more people own a car, and less people are in cities. And we're talking about a company that is primarily marketing and software, where the wind can change very quickly, and assets are mostly intangible and untransferable.
car manufacturing is much harder to get into, so having a factory and an almost-complete design is already a huge milestone. Obviously, they'll need to sell _some_ cars, but they could even make money if they were to sell cars at a loss, through carbon credits.