In the USA, a lot of people are still "conditioned" to buy from a carrier store, going back over 20 years which is where
people started buying phones. Plus, people think they are getting a good deal for a "free" phone by a carrier locked
phone, but actually pay MORE than if they had bought it outright.
The last carrier phone I bought, was the original Samsung Galaxy on AT&T.
I switched to straight talk not long after and did some calculations of using an MVNO, vs a carrier locked phone, over the
course of the contract.
I've been on an MVNO ever since.