I totally agree with you, for me there is no reason to use the Cable box.
But, I also do know that not everyone can do that physically or legally.
So if it is possible for you to use a internal DigitalTV card you can do that. The downside to this solution would be lossless recordings, better integration, lower power use, one less remote and so on
What you will lose are functions that your provider gives you on your Cable box, like Pay per View, channel specific buttons and EPG. The EPG in myth is a lot easier to use for recordings, and Pay per View can usually be done by phone.