I can only assume they know but can't fix it.
In fact, why isn't there "adjust volume to surroundings" like there is for brightness? They should KNOW how loud is appropriate based on mic input.
Maybe it's for people who drop their earbuds? So it can be heard from a distance? That would certainly explain it...
A hack would be to put some foam or so inside to dampen the sound and then max out the volume. Then they physically cannot make loud sounds.