Putting antennas up high is a remnant from TV days. The difference between
25,000 miles from the ground and 24,999 miles, 5260 feet from the roof is
negligible
Just like the TV antenna, you put it high to "see" over terraine, buildings,
and trees between the antenna and the signal source. Sometimes you can
achieve that with something on a 6' pole in your yard and sometimes you need
it on your roof.

I notice the "yard mounts" in places where the disk "looks" across a public
road which means that trees are far enough away that they aren't a problem.

In a town house community I am familiar with, the "dish" folks put them at
the peak of the roofs. I suspect that among other things it keeps folks
from screwing with it.