I occasionally turn it on just because I like the GaP music. Also, the world map music is great for using as hold music if you just leave your phone in the room while you go to the bathroom or something.
I generally turn game sounds down (or off, in this case) due to the fact that I’m also listening to something else at the same time.
I will keep sound on for games that need full focus but GoW end game is just grinding so it gets only a small bit of my attention. And only in short bursts.
(I should have included a bonus option to ask, how many players know, that the Gnome Rush has its own musical theme. I certainly did not until this thread.)