I'm somewhat sure that the low contrast predates advertisement on maps by several years. I also doubt Google would willingly compromise Maps's usability for the sake of advertising, especially right from the start where there is enough low-hanging fruit and revenue is bound to be negligible. That would be like plastering ads over the google.com homepage, something they continue to resist two decades in.
My money is on either a wish to make (all kinds of) labels stand out, or just aesthetic preferences. FWIW I always found OSM to have too much contrast (and too much details), and the emergence of all these services rebranding OSM in different styles would seem to be evidence for other people also considering OSM's default style to leave room for improvement.
My money is on either a wish to make (all kinds of) labels stand out, or just aesthetic preferences. FWIW I always found OSM to have too much contrast (and too much details), and the emergence of all these services rebranding OSM in different styles would seem to be evidence for other people also considering OSM's default style to leave room for improvement.