Why would you have both DirectTV & cable service

Or am I more confused than usual
I compared channels for my area and DirecTV not only has more (and more in HD) but many come in east and west duplicates. Like CBS & NBC (and some premium show channels) may show a program at both 7:00 (east coast) and 10:00 (west coast) local time. So, if we miss a show at 7:00 we can catch it at 10:00. Same with channels like HBO, Showtime, etc. there are east and west broadcasts. Usually not the same shows repeating like network stations but it does double the shows available.
The only two networks I can't get due to some kind of regulation are ABC and FOX. If something is on those I can still watch it on basic cable particularly when the weather is bad we can tune to the local ABC station. Those stations and cable internet are all I use cable for now. I'd never use satellite for my internet connection. :noway:
We have two TVs on DirecTV and each can be watching different programs (and each can be recording another program) where I'm not sure if cable will allow two TVs to watch different stations...not sure on that one. We have a 3rd TV in a guest room with our current basic cable and setup for an XBOX but it's rarely used anyway.
So, essentially it's cable for Internet connectivity and two local stations and DirecTV for entertainment and from what I've looked into so far, (our) cable doesn't provide the same viewing flexibility.
We're really thinking of the cable phone service since basic cable/internet & AT&T phone is more than the package offered for basic cable/internet/phone from our cable company.
Since DirecTV requires a land line phone to update programming software, I'm wondering how the cable phone service would work with DirecTV.