Comment by andrewflnr

I mean, it still can be idiosyncratic if the local maximum is steep enough. Identifying and signalling subgroups of mitochondria in a cell to put on pause might be prohibitive, for instance, and would still reduce the power available to that cell.

Or maybe going all the way on and mostly-off with your mitochondria, even specifically with your brain mitochondria, really is that much more efficient than having half of them offline (but still consuming energy for upkeep) at any time. The brain is a big ol energy hog, after all.