Mark Evanier makes a good point about TV networks that don't start or finish TV shows when they say they're going to. I often catch myself thinking that networks should try harder than that to keep their viewers happy. Then I remember that we're not the customers. Advertisers are the customers, and viewers are the inventory. Businesses don't spend much time thinking about what they can do for the benefit of their inventory, as far as I can tell. Viewers aren't supposed to be taping or TiVoing shows, we're supposed to be watching them when the network wants us to, letting them wash over us, commercials and all, like good little well-behaved consumers.
Some networks are more courteous on this point than others, but the ones who aren't have little reason to want to do better. Not zero reason, but very little.
It was a little different when broadcast networks dominated; frequent on-air switching between network and local programming made it necessary for everybody to keep to a strict clock.