At least where I work, RSUs are often dangled to you as a way to justify a lower base salary. RSUs are built into the 'compensation philosophy', wherein the RSUs are combined with salary to calculate total compensation.

You're underpaid with regard to salary, so you'll lose a lot more by foregoing RSUs than you would if you were just paid a fair base salary without RSUs.

The other day I was talking to my wife about my frustrations at work, and she said "Well, just don't quit before you get that RSU vest." And I'm sure I'm not the only one who has had such conversations.

Since all companies assume their stock will go up from time of issue, you may have been promised $100k in stock that is now worth $200k. So your initial "cash" future promises are now worth more. Lots of people at e.g. Meta are in this situation since their meteoric rise.

You shouldn't, but that's the psychological trick at play.

They are betting that your loss aversion will tip the balance a little in their favor.