Why was the "Power save" mode removed?

May 8, 2013
I mean, I always kept my Mi2S in that mode and it lasted for almost 2 full days with the 3100mah battery, now that it has been removed my screen gets crazy hot, and the battery won't reach the end of the day.
It was said that it was removed because of "reasons", but I really can't see these reasons, I'm not going to update my phone and I'll sit on my 4.7.4 because there is really no reason to update now, it's scary how much it gets hot and I really can't trust the newer roms.