Earlier quoted context omitted.
At this point, anybody offering those terms is well-aware it's not in the employee's best interest. And they don't give a shit. I agree, 90 days is totally ridiculous.
A 90-day window might be better for you if you want to stick around at a company for a while and there were other people that came before you, but left. "Dead equity" of startup employees who have left but not exercised means that they can let you do all of the work while they dilute the available equity pool (i.e., take money directly out of your pocket). This a16z article goes into this: http://a16z.com/2016/06/23/…
I don't know many people that go into a job not wanting to stick around for a while. But that's at the beginning of the relationship, when everything is rosy. After the honeymoon, if it turns out that the company is toxic, things change.
"They're your employer, not your parents."
This statement makes no sense. That doesn't mean they aren't obligated to act ethically.