Tell me about human psychology -- You sign onto a job with no promise of getting a bonus until you work, say, 90 days. What does it matter if you got fired 1

Tell me about human psychology -- You sign onto a job with no promise of getting a bonus until you work, say, 90 days. What does it matter if you got fired 1 month before that date, versus 1 day? You feel it was almost yours, and it feels so much worse? Aside from that, until workers refuse to sign up for a job that has a 1 month vesting period for the bonus, and instead they have to make it 1 week to find employees, or 1 day, what is there to object to? You agreed. Of course, I am not known for my PR skills.