They don’t. But it’s a lot less paperwork. One little marriage license handles all the powers of attorney and wills. You don’t need executors if your brand of reality is simple. Everything I own goes to the wife if I die, because we live in a community property state and technically I don’t own anything, WE own it all, and if I die it’s hers and all done. Now if I wanted stuff to be more widely distributed, like if we had kids, or I had an ex, or a favorite charity, then yeah I need a will and an executor and that junk. But I don’t, so I don’t. And most people actually live in a fairly simple version of reality.
Yes it can be “handled” with extra paperwork. But it’s handled for TENS OF MILLIONS of couples through a marriage license. And was for centuries before anybody invented palimony and started with the trouble of faking legal marriage.
Oh that's just precious. Naive. Totally wrong, but cute in a pollyanna way.