The problem is that the increased efficiency is offset by software/OS that uses more power, as well as often a physically smaller battery. Apple, Samsung, and all the rest have basically decided that current "all day" battery life is good enough for most users so they don't actually try to make them last any longer. If they make a breakthrough with efficiency, rather than use it to make the battery last longer, they'll make the battery smaller to make the phone thinner and lighter instead.
Personally, even though my 14 Pro Max easily lasts through a full day and then some, I would love for it to easily last 2-3 days or more.