The pressure is from the content providers, not the cable companies per se. Viacom, for example, owns dozens of channels. They don't want Comcast to sell the channels individually, they want Comcast to provide the channels to every subscriber and pay Viacom for every subscriber they provide it to. And they want Comcast to do that with all their channels, not just one or two.
So, the meeting goes like this:
Comcast: Most people don't want MTV any more. We want to make it a-la-carte.
Viacom: Nope. You want Comedy Central and Nickelodeon, you're going to carry MTV too.
Comcast: Well, we wouldn't want to lose Comedy Central or Nickelodeon but we really want to do a-la-carte for MTV.
Viacom: Well, okay, but the price for Comedy Central and Nickelodeon just went up to total more than all three did before so your customers are gonna be kinda pissed that their prices went up and channels went down.
Comcast: That's robbery!
Viacom: That's business.
Comcast: Oh. I guess we'll take all three then.