Perhaps, but that pipe stays in one place at all times. It doesn't provide the capability of delivering your e-mail and offering you internet access practically anywhere that you are. that's a feat that requires a lot of work and a lot of equipment, moreso than a DSL or cable modem.

Most people also pay only a few bucks a month for flat rate local phone service at home, and yet they pay more for cell service. There's a reason for this too.