Don’t forget that federal regulation limit how much compensation the airlines can offer someone to bump them from a flight....
Not to mention all the other federal regs that increase the cost of airlines that contribute tot he airline culture of constantly trying to overbook flights....
Airlines can and do offer more if necessary.
The $1350 is not a maximum limit. It is a minumun threshold. If this threshold value is met or exceeded and still not enough passengers accept, airlines can start involuntary bumping without legal repercussion.
Stop reading and believing fakenews. There are plenty of knowledgeable sources (aviation law attorneys, for example) that have provided useful analysis of this issue.
The airline offered vouchers for another flight on UNited — if you got bumped off, would you want that? If they offered cold, hard cash, more people would have jumped.