In that environment the founder has no hope or reason to go public, making equity in the company worthless.
VC used to push to public exits in order to maximize the founders and VCs stake which turned employees equity to a liquid asset. Truly aligning everyones interests, nowadays not so much.
You're forgetting about dividend, and off-market trade.
If a company is worthless if it isn't public, then IKEA would be absolute garbage. Quite strange for a company making hundreds of millions in profit for its owners.