Obviously I can't speak for Rob or Hugo et al, but it might not be worth it. The tweak might not affect the battery life much at all. If it were only 10-20 minutes less than the nominal 18 hours then it might be worth them spending development time on more desirable features and fixes. If, on the other hand, it affected the battery life by a couple of hours, then that idea has merit.
I wonder whether it could start with the 'active' setting when you started playing and optimise towards conservative on the fly. I suspect that the KISS principle would apply here.