That doesn't answer my questions although I now realize I made a bad assumption. This is a modern technique. I misread the bit about Greece on the wikipedia article and somehow got it in my head that it was more ancient.
So I think to answer my question more directly, yes, it's just copyright laws.
My point, before understanding that, was that from the map consumer's perspective it doesnt make a difference. And from the original creator's perspective it has a little accuracy cost. So without an additional mechanism I didn't see the disincentive for copiers. So I wondered if it was some ancient form of copyright law or just strong sense of morals or what.
So I think to answer my question more directly, yes, it's just copyright laws.
My point, before understanding that, was that from the map consumer's perspective it doesnt make a difference. And from the original creator's perspective it has a little accuracy cost. So without an additional mechanism I didn't see the disincentive for copiers. So I wondered if it was some ancient form of copyright law or just strong sense of morals or what.