Heh, it's all about setting those expectations. When my wife first moved in with me, I had a front projector setup with 5 speakers (2 front towers included) in a studio apartment. The receiver *had* to be turned on because the projector had no internal speakers. We have moved twice now, and I have changed my setup around a bit (I think I've upgraded receivers twice, and gone through a couple of speaker configurations) but she has been used to turning on the receiver from day 1. She loves watching movies (checks out DVD's from the library and usually watches 2 or 3 a day -- we don't have cable and never watch actual TV) and I think the sound is a big part of that. She doesn't like to crank it super loud, but I can often hear the bass from way in the other room.
IMHO a receiver is actually more convenient than switching sources on the TV. At least with the receiver you have direct button access to any source; with a TV, you usually have to cycle through them with a single button.