You must be young.
Remember, just because you don't see a need for them doesn't mean the rest of the world feels that way.
Apparently you don't remember when phono inputs started disappearing from receivers. Many didn't notice until after they bought one without them.
This would make a lot of sources impossible to use with them. Turntables which are making a comeback in some circles, particularly with hi-glitz phono preamps, but a lot of people find those red/white inputs handy for things like a quick-and-dirty Ipod connection, some die-hard VCR users still cling to life (I'm one), not to mention a few still like tape decks and whatever else you can think of.
Also, remember, tuners are by nature an analog audio source, so putting a few plugs on the back and incorporating switching is not a big deal. Being backward compatible is a good thing.