It does make sense becvause on some worlds you cant get to other worlds. The Gate on earth can go anywhere, but on other gates you can only go to a certain number of other worlds because the DHD's have different gliphs on them., Remeber in the episode where SG-1 is stuck in the off world prison? Daniel tries to get an adress that the Stargate will be able to dial because there is a limited number of gliphs on each startgate.
Also on other occasions SG-1 has lost there remot transmitters and have had to find other planets they could go to, but they had to rule out some because the stargate couldn't dial certain planets.
Also if all of that didn't make sense. planets in orbit around the same sun, should be able to have the same home glyph, such as each state has its own area code.
That was pretty confusing....but It makes sense to me.