Explain me resolutions

[georgir]

I'm a little confused, why should the dvd format and its successors enforce only a given set of resolutions as standard/allowed?

I can understand that in the age of analog television, the signal had to be exactly a specific size to be displayed by the TV. But now with digital video, rescaling the image from any resolution to any other is a simple process, so why aren't arbitrary resolutions allowed in the DVD standards? We do have a bunch of DV resolutions already anyway, with PAL and NTSC both having 4:3 and Widescreen variants, and the lots of HDTV resolutions. So, chances are, in a lot of cases your player is doing a rescaling of the image anyway. Then why not allow all resolutions?