Over the last couple decades, companies have been buying all kinds of databases and corellating the data in them. There are public maps indicating which roads are where, there are real estate records indicating where houses are on the roads, and there are phone books telling who lives there. Some of the data was easily available on-line, some of the data had to be meticulously typed in and/or reformatted into a usable medium. In some cases - such as the door-to-door GPS marking - they just had to go out and physically get that data. It was a lot of work. Eventually, all that data starts to come together into a (mostly) complete, comrehensive, easy-to-process form where (say) Tom-Tom can just buy a database of addresses and dump it into a fat (but cheap!) memory card in your car’s GPS device.
As noted elsewhere, this data is not always accurate or correct, and some of it is old enough to be out-of-date/wrong. Most of the time your “GPS knows exactly how to get you to any address”, but sometimes it’s wrong - really really wrong (as not long ago I was looking for a town and my GPS dumped me in a middle-of-nowhere forest on a one-lane dirt road). Ergo, in the government tradition of taking its obligations too far, the Census Bureau is now making that information very accurate by literally sending agents door-to-door to exactly marke each and every home.
Thank you for condensing that down. And yes, I’ve had the same issue with my GPS. It usually knows how to get me places, but for some weird reason, when I drive on the Sawgrass Expressway between here and my friend’s house in Coral Springs, it tells me to make a U-turn and go back at ever exit! It just really wants me on I95 (which is way out of the way!).