[TimJRobinson]

It's a database optimization. Whenever you send funds that entire UTXO is destroyed and redistributed to new ones. Because of this you can easily calculate the current state of Bitcoin by only looking at the current UTXO set, and ignore all the old destroyed ones, instead of having to go back in history and see who sent what where.

It also allows for easier parallel processing because you can check many UTXO's in parallel without having some shared state they interacted with.

Only a few chains use this system - Bitcoin, Litecoin, Cardano, Fuel, maybe some others. Almost everything else uses an account based model, where everyone has an account balance, like how you'd imagine a blockchain whould work.