The MAP can be copyrighted. The DATA on the map cannot. Just because you’ve made a map of a city doesn’t mean somebody else can’t.
Do they map it out themselves or do they simply redraw your map?
Some map companies deliberately include some errors (naming etc) to catch misappropriation.
The same is true of music and film index information (label stock number etc or all the movies someone has been in).
You can’t simply good to discogs or imdb and lift that information to source your own commercial website.