It's about control
If you could actually download and replay their shows (past the poxy 7 day limit), then it follows that you can choose what you want to watch.
And if you can choose what you want to watch, it follows that you won't watch the overwhelming majority of shit programs that make up their schedule on an average week.
What I find interesting is that since TV stations have started putting their shows on Youtube, (particularly Channel 4), their ratings (recorded by the Youtube view counter) have been terrible. A couple thousand views on some shows. And the large majority of those people hit the "thumbs down" button.
TV execs are finally realising that all these years they were talking about having millions of viewers, fuck all people were actually watching. Fast edits and minor celebs does not a good TV show make.
Their solution to this, of course, is a misguided attempt at controlling the viewer. They think that they can just force us to watch their crap shows. But they forgot one thing: they have already failed.