Well, generally, you tell the TiVo to record shows by name, not by time and channel. The guide tells the TiVo when those shows are on. You could set your TiVo to record by time and channel alone, but then you lose lots of what's cool about the TiVo. (In reality, though, I think they restrict what your TiVo can do when you don't have an active subscription, and it may prevent you from using it to record by time and channel like that. I can't remember now.)

Anyway, what I'm getting at is that the guide isn't so much for the user, but for the TiVo itself, so it can see what to record. It also actually includes way more stuff than is shown on the GUI, so you can set it up to record by criteria you wouldn't actually be able to find anyway, like movie directors, or guest stars or whatever.