This is literally still how it works. Instead of a contract you have a device payment plan where you're defacto locked into the carrier because if you leave you owe the balance on your smartphone.
The trade-in and switching deals are all done as bill credits so that you are locked in for 2 or 3 years.
If you are using a big three cell carriers with the unlimited postpaid plans and aren't getting a brand new latest model Pro phone for free you are throwing your money out the window, because you're still paying for the phone in your higher plan price.
You will almost certainly save money if you buy the device yourself and use an MVNO instead of the big three postpaid plans. Especially if you buy the device used after it depreciates for a year or two.
The trade-in and switching deals are all done as bill credits so that you are locked in for 2 or 3 years.
If you are using a big three cell carriers with the unlimited postpaid plans and aren't getting a brand new latest model Pro phone for free you are throwing your money out the window, because you're still paying for the phone in your higher plan price.
You will almost certainly save money if you buy the device yourself and use an MVNO instead of the big three postpaid plans. Especially if you buy the device used after it depreciates for a year or two.