Perhaps you aren't old enough to remember how home phones used to be. You paid per call up until the 70's, and even then, you had restrictions. The unlimited local calls did not become a standard in the land line phone industry till the late 70's early 80's. It wasn't a bandwidth issue in those days, since each phone call required a direct connection, but instead it was a switch board issue, only so many calls could be placed on any system at any given moment. And don't even get me started on party-lines, good old Mrs Snodgrass used to love listening in on my families phone calls!
The unlimited plans are the future, it's just harder to play catch up with technology these days, it just moves too fast!