Remember the VCR? Oh, the picture quality wasn't great, but it had one major advantage: you could record a show on a physical medium that survived even if the device that recorded it failed.
Today, we have the DVR--a totally device-dependent means of saving shows that makes it impossible for you to create useable backups that can be viewed on other media. Unless you have the means to record programs on your computer and then back them up, there's no practical way to save programs from your cable DVR, satellite DVR, or Tivo in any form other than on that machine. And that means that it is absolutely guaranteed that, at some point, you're going to lose some of the programs you want to watch.
So far, in the almost ten years that we've had DVRs, we've had six units fail. Some of them have failed in less than two years, some have lasted almost seven before going dead. (Oddly enough, the longest-lived unit we have is a Motorola DVR from Comcast; we got it in 2002 and it's still plugging along, so that probably means its days are numbered.)
"But we have DVDs and iTunes and the Amazon store," people will say to me. Yes we do... but I can absolutely guarantee you that there are shows on some of my DVRs that have not been (and most likely never will be) offered on DVD or via digital download. Conversely to what many people would like to believe, not every program attracts the sufficient number of viewers and/or audience demographic to make it worth producing for sale--and in some cases, rights issues make sales problematic. Also, news programs are hardly ever offered for sale on DVD, because most people have no interest in viewing old news broadcasts. Same for a lot of local programming.
While I have the ability to dub off some of my DVR programming as an AVI or M4V file, I would venture to guess that about 90% of all television viewers have no ability to do so, nor the slightest inkling of how they'd go about doing it.
It's ironic that I still have a large library of programming from 1977-1985 that I can view when I wish to, but I have no handy, convenient way of maintaining such a library today. Of course, that's just what the networks and programming providers wanted, I'm sure...