As there ARE lights with this feature, the end result of whether they SELL or, end up on the clearance rack, will be if the feature is as important to THEM. If so, more lights will follow suit.
If they languish on the shelves, makers will drop it from the features list.
It seems to me that WE are on the cutting edge, and that WE are NOT joe user.
Personally, I have found the Brinkman battery indicator more useful, than the Nitecore MSC20 one that flashes Green or Red when I turn it off. I be willing to bet, that at the manufacturing level, that it would cost pennies, OK, maybe a hundred or two, to add battery charge indicator features to a light. I'll predict that we will see more in the future. Let's face it... it is a selling point. Joe user doesn't know throw from flood, but can recognize a "battery charge indicator" in a heart beat. That would make one light better than the next.
Hmmm... two lights, what's the difference... oh THIS one has a battery charge indicator--- I'll buy THIS one.