Thing is, they predate the hill forts, so, the idea that they're indicator/maps holds good when the population is numbered in the thousands and not the millions, and warfare over territory, resources and people isn't yet an issue.
Hillforts start in the rBonze age but really come to the fore in the Iron age.
Megalithic art such as the cup and rings appear to be meant to be seen, not hidden away in caves for only those who made them, braved the dark, or endured some ritual. Markers of some kind, whether maps or remembrances; lots of theories, lots of ideas, but apart from stylistic development and contexts and comparisons with others, we really do know very little about them.
Sometimes I think it best just to think of them as a "We were here, we were a people, we lived on this land", kind of thing.
It's an incredibly ancient habit this pecking marks and rings on stones by humanity. We have them from at least 100,000 years ago (remember Scotland's landmass was scraped clean by the ice, and that only retreated about 10,000 years ago) and we know that Neandethals used them too.
Some (elsewhere) are clearly used for pigments, some channel water in a 'flow', many have been reused in ritual sites and yet others are literally musical instruments. The rocks sing as they are struck
but then we know of hand carved bird bone flutes that are at least 30,000 years old ( Hohle Fels cave).
Loads of links for more reading, but some I've read recently are.....
http://www.archaeology.co.uk/articles/features/trefael-the-dolmen-that-became-a-standing-stone.htm
http://www.academia.edu/7769868/Por...p-Marked_Stones_and_Prehistoric_Rock_Carvings
I sometimes wonder what our ancestors would make of our music and of our road network
I think they'd approve of the boots though
M