They could get their money back by (gasp) getting their share of the company profits. Which is actually how it usually works outside of SV-like investments.
Early-stage investors and dividend-collecting investors are not the same. They might be different parts of a single portfolio, but they're separate strategies. Switching from one mode to the other is something public markets are very good at. If a company wants to pay dividends instead of getting acquired, it should go public and start paying dividends.