For most of us, our needs are mostly two things.
Battery small enough to afford, and battery small enough to carry.
You bet, it would be great to charge to 4v, and stop at 20%, but to get very far you'd have to carry a huge, heavy, and more expensive to buy battery. Bear in mind, those nasa and military batteries are not usually running an EV. Their needs are different. Double size battery might mean 5 ounces, not 5 kilos.
But hey, if your ride is 5 miles to work, and can charge there, hell yeah do it.
Back when I commuted, I did 15 miles then charged. Downhill to work, it was usually a 60% discharge there. Coming back, depended on the wind. Often enough in winter, 95% to get back up that hill into the wind. My battery charged to 100% twice a day. That was my needs then, ten years ago. Whatever I could gain charging different was offset by my need to be able to ride in the am, with no fuss. I'd leave the house in the dark so not convenient at all to even top up in the am.
Now retired, I do a lot of 10 mile rides, with a pack that could do 20 miles, or 10 miles full speed (35 mph) I have lots of time to charge before each ride, and the typical deal is a 50% discharge and then storage for a few days at that half charged or less voltage. I charge to 95% or so, 4.15v. I could charge less, but my 50-90-100% charger finally died after many years hard use. If I do discharge deep, I just zap it a few min to bring it up from empty before storing it again.
FWIW, the pack is naked lipo, 18s 15 ah. Its two years old, so getting lower capacity and higher IR.