So many times I forget to plug the deck or someone uses the charging cable for something else and I come back to play the next weekend and the deck is at 0%. Why doesn’t the deck have a deep sleep or hibernate mode on by default like my laptop or iPad?
Most of that is really old knowledge from before the days of sophisticated charge controllers.
Maintaining a high SoC is still very damaging to battery life.
Which is why the charge controller does not do it. It will drop to a sustainable voltage when it detects longer wired connection after being charged and adjusts the “percentage” it shows you accordingly so you still see a 100 to 0.
Do you have anything to back that up with or are you speaking from personal incredulity? What you said certainly does not apply to e.g. contemporary smartphones.