So what do you do if the checksum doesn't match? Could be off by a meter or half an Earth. So the only recourse is to send it back. Normal addresses are far more resilient. Wrong post code? It'll get re-routed and just takes a few days longer. Wrong house number? In most cases the mailman knows the names in their area and will still deliver it. Typo in the address, name, city? In most cases it still works fine, the example of enkrs notwithstanding. Letters get mangled all the time, and mail still arrives.
Also I'm much better remembering addresses of people instead of their GPS coordinates, especially when they're close together, like in a city, where the coordinates would all be almost the same.
I specified adding multiple more so you can use the checksum to repair the number. If they get three or more digits wrong, well, they could have put the wrong city name on there too. In the realm of transcription errors, it's easy to make coordinates work. It's remembering these addresses that causes the real problems.
It's far more likely for someone to screw up writing digits than it is for them to write the wrong city name. People handle words well, but they don't handle numbers all that great.
And if they do write the wrong city, well, that's what the zip code is for.
Also I'm much better remembering addresses of people instead of their GPS coordinates, especially when they're close together, like in a city, where the coordinates would all be almost the same.