In order for them to leave they would have to sell their shares and it would be possible that those shares would spread to more people. This could broaden the number of shareholders. It also allows the corporation to continue indefinitely as long as the board of directors through the shareholders keep the right leadership in place.

It is hard to buy IPO stock at the IPO price. There are IPO etfs out there and those people are better at buying IPOs at the starting price, but those ETFS invest a lot of different IPOs not necessarily the one you want. I wish you could just go on Robinhood and buy the IPOs at the start.