This is competitive pressures at work, similarly to IBM and other's investment in Linux in the early 2000's as a way to place competitive pressure on MS/Windows. If you're not the leader in the field, and won't be able to catch up just by investing, you try to make the leadership in the field (Google's) irrelevant. If the 2nd-best-by-small-margin base map info is open, having the best one isn't a competitive advantag…
Second best? At least in my experience, OSM data is leaps and bounds better than Google Maps in every way possible, and it has been that way for a couple years now. The reason that I still use Google maps is that it's fast and well-integrated with my phone, and it has a lot of added features on top of the actual mapping that makes it very useful --- things like location sharing when you're on a longer road trip, crea…
I'm sure that, for whatever product in the world, you can find a subset of people in the world who will swear that such product is, in they experience, the best in the world.