The problem is that consumers want to buy a phone with 24 hours of runtime and an EV with 200 miles of range, and they want the phone to be thin and light and the car to be fast and light, and manufacturers want to achieve those capacities with as little electrochemistry as possible. The number of charge cycles at full capacity will be a big deal a year or two in, but on the sales floor it's a secondary concern for typical buyers and sellers.

Playing fast and loose with the numbers, I'm sure that if 100% on the display was 80% in the battery and 0% was 20%, you'd have an amazing number of charge cycles. You could program that 40% of unused capacity to be reduced as the battery ages very slowly, and by the time the used capacity is only at 80% of its original revealed capacity you're at many thousands of cycles. But you'd have a phone or car that weighed 40% more and cost 40% more than one that had no buffer and ran at the bleeding edge on day 1.

Absent breakthroughs in battery chemistry, this basically regulates the amount of buffer capacity that manufacturers are required to include in their ~~lies~~ marketing materials.