Use a lock-up (like public markets) or have the preferences expire / reduce (like the contracts some banks gave pre-IPO Uber employees). Or be like Softbank and demand a 7% dividend on invested capital. Or if you don’t actually have a constructive relationship with the founders, don’t invest.

The only warrant for preferences is for fueling carry and information arbitrage within the VC circle. There is zero benefit to employees, who thankfully know more today.