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?
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.
Contemporary smartphones tend to push things a bit harder to offer the “best” performance in the first few weeks. Though I have to say comparing today’s newest phones with phones from 2015, battery management has gotten a lot softer.