This sounds like a good idea at first[1], but then you realize that text is often accompanied by graphics that are not vectorized. Resolution independence when coupled with raster images is a hard problem. You can render the text at the desired size fairly easily, but you can't resize a bitmap arbitrarily without it looking pretty terrible. This is why resolution independence hasn't happened for displays despite lots of attention. It's also why Apple just doubled everything to keep it simpler.

[1] Actually, it might not even seem like a great idea at first if your first thought is to contrast your phone screen and TV screen.