For 30(?) years since the invention of stock options there has also been a de facto added protection against high turnover in infancy-stage startups, where having to rehire and retrain employees is extremely costly. Pre-IPO you basically had to pick a team and take it to that level of maturity before you could leave. You couldn't hop around seed-level startups without giving up your options, usually.
What's changed now is startups are staying private longer, leading to unfair scenarios. E.g. you're at a >$1B company with >100 employees for 6 years and you still lose your options. Traditionally a company would have gone public by that time, but now it's not, so we need a fix.
But if you overcorrect and now eliminate that added protections for younger startups, you risk creating an incentive to leave companies just for the sake of options portfolio diversification. Why bet on one team when you can bet on three, since even 1/3rd of a unicorn that makes it is worth more than 100% of the one that doesn't. And that individual decision leads to higher turnover which can kill infant startups.
Bottom line this fix should be more carefully targeted at what has changed to exacerbate unfair situations, namely startups that have reached "should be public" levels of maturity, yet are still staying private.