[genocidicbunny]

They still exist, but I think these days there's a bit of confounding with carrier-subsidized phones. The phone isn't technically locked, but if you switch carriers before the subsidy has been paid off, you owe the remainder of the phone's price -- usually it's rolled into some kind of Early Termination Fee.

There's also some amount of regional locking, some phones might not be licensed to operate in the US but are in Europe, or vice-versa.