From the link I posted above:
“As you can see, in many cases you’re entitled to a sizable cash payment, up to $1,350. However, here’s the dirty secret of the airlines. In a vast majority of cases they’ll only offer cash compensation if you specifically ask for it. Otherwise they’ll offer you the same voucher they gave anyone who was voluntarily denied boarding.”
Involuntary bumping and you fall under statute and they can ask for cash.
Voluntary bumping is different, I think you’d be under the category of funny money like miles, 1st/business upgrades, etc.
Still better than being put in the hospital.