I think the idea is if you programmed your laptop to never charge the battery past 80% or discharge it past 20%, it would degrade much more slowly, but you would also get about 40% less battery life out of a single "full" charge. Or you would need to increase the battery mass by 66% to get the same battery life. Laptops need to be light enough for a human to carry, while cars don't, and cars are generally expected to last longer than laptops, so the second solution is probably more viable for cars.