Most public restrooms that I've used (in the US) place the paper holder very low, with the bottom of the roll (where you can grab the paper) below knee level when seated. This is not true in the stalls outfitted for wheelchair access, where the roll is higher. Fixtures in private homes also seem to generally be at least a foot higher than these low-hanging ones.
Whom does the low placement serve? One generally has to lean forward to reach (especially since fixtures in public restrooms tend to be enclosed, not just a roll hanging on the wall), and it doesn't seem that it's a convenient height for anybody who is old enough to use the facility unassisted. This is a change I have observed over the last 15-20 years (it wasn't always this way), making me wonder what's driving it. Is there some use case or design trend I'm unaware of?