Not the first one to bring this up, but I figured I should voice it and add one more reasoning to it:
1. Sometimes I just want to listen to some ambience music in the living room and don't need the fully-fledged surround system to kick in.
2. Having all speakers on st all times = higher electricity consumption
3. For casual TV watching the surround is overkill
4. One should at least be able to turn off the surrounds without having to see the green blinking lights at all times