[jerlam]

A lot of people are still on ancient plans like $80/5GB since they don't know they can change providers and still keep their number. Or they're old and avoid changing any aspect of their lives. The mobile companies are fine with "grandfathering" these customers.

[HDBaseT]

Mobile companies will never, however, grandfather plans which have better value. They will happily grandfather more expensive plans, hell they won't even tell you.