Not just a question of worse coverage and providers
While it's true that US mobile providers have worse coverage and price plans, I think the most important factor that's slowed growth in the US mobile sector is the fact that in the US you don't pay for local calls made on a landline. Given that any landline you pay for will have unlimited free local talk time - erm ... why would you bother with mobile call charges and texting, exactly? In addition, what counts as 'local' will sometimes cover something like 1/4 the size of the UK.