Why is polygamy illegal?
Lawyers haven't found a way to exploit it yet.
See, if 2 people get a divorce, then there's half of everything, and that's a big chunk for the lawyer to work with.
But, if 3 people get a divorce, that's only a 3rd of everything per lawyer.
This continues ad nasuem: if you have a rockstar with 100 wives, that's only 1% of his wealth sniped by a gold digger. What kind of tabloid headline would that make? "Golddigger wants divorce, wins 1% of Brad Pitt's fortune!"
So you see, preposterous. If it bucks the trend of lawyers taking all the money, it ain't gonna happen.