Seems like the gang here isn't getting it speedknot. Sorry...
The problem is that he wants his family to be able to use any source in their lineup, at any time. Not just cable TV. So, gaming, and possibly streaming apps, etc. So, he can't just switch it back to cable. I know with Denon you don't even have to remember. You can just set the receiver to default a specific source to passthru when the receiver is off.
But, that won't give them access to the other sources. Which is why a universal remote makes the most sense in this instance.
Not only that, the entire purpose of using good speakers in you get better clarity at lower volumes so instead of a shrill tiny TV speaker, you get clear audio from proper drivers at lower volume. It enhances everything from news broadcasts and YouTube videos to Blu-ray Disc and HD gaming.
It is possible to plug everything into the TV and just use optical audio output, but then you lose your HD audio formats.
Literally, a A/V receiver is ONE more button to press. Turn on source, turn on TV, turn on A/V receiver. You either have to switch the TV or you have to switch the A/V receiver to the proper source. It's not that complex, but it is so easy for a universal remote control to handle. Press ONE button instead of 3 (or 4) and you are there.
More importantly, it actually solves the full scope of the request which was made by giving the entire family full access to all the sources which are available to the room and keeping is simple to operate.