They are the size they are because cable was SOOOOO BAAAAADDDD! Both sat services were so greatly superior to cable, including customer services, that both Dish and DirecTV poached from cable, NOT many first time payTV customers except for rural, but the big numbers for sat in actually in areas served by cable TV. Competition and superior PQ and everything else from sat is why they are big.
That's largely no longer the case. Cable as an industry has closed the gap over the last several years.
It all depends on your operator, but if you're getting digital service, and most cable operators have converted to all digital, the picture quality is virtually indistinguishable from satellite. Also technology has come to cable, which now routinely offers whole-home DVR service. And regarding price, because cable also furnishes broadband and phone in many areas, they can bundle all three services and charge you less than you might pay if you subscribe to satellite and cobble the others together.
Satellite's major advantage now seems to be for the sports fan, in being able to offer out-of-market regional sports networks, as well as season packages such as NHL GameCentre. Either the cable operator can't spare the bandwidth or doesn't want to pay the leagues for the access. Also benefiting are folks who can't get enough HBO or Showtime channels. Cable seems to offer fewer of those.