@millercarbon Are you suggesting I replace my center and surrounds with subs?
FWIW I already have 4 subs.
Excellent. Its not so much suggesting replacing center and surround with subs. Obviously they serve completely different functions. The suggestion is more there are better results to be had with stereo than HT.
If all you are doing is watching movies and watching movies only then surrounds might make sense. Watching movies is primarily visual and so the loss in sound quality is hardly even noticeable. Especially since its never compared with anything but video sources.
You however are also listening to 2ch music. In this case surrounds and HT in general is full of downsides with not a single upside anywhere to be found. Already you are running into them. I fought them for years before finally realizing even the movies sound better with 2ch than surround. So my suggestion is transition from HT to 2ch.
For example you could right now have better sound simply by running 2ch from your video source direct to your stereo pre-amp, cutting out HT altogether.
As to your exact question, whether it needs to be on or not, yes this is just a design choice.