I remember when I was looking for a new laptop, I made a replaceable battery a requirement, since my previous laptop's battery (which wasn't replaceable) lost its charge very fast.
Out of the hundreds of laptops available today, I could only find two or three laptop models total with a replaceable battery. And none of them were in physical stores, so a less tech-minded person would never find them.
Interestingly, the replaceable battery also seems to be higher quality than the permanent battery was.
If you shouldn't charge over 80%, why don't manufacturers just report a battery at 80% its "real" capacity as 100% charged? Same for the lower margins. It would probably make things easier for people to understand.