They used to use some data from osm, public transport in some parts of Poland, and they displayed the required attribution correctly:

https://xcancel.com/MapAmorePH/status/1453863816110952450

I have a feeling, it's just some users who copy from osm to gmaps, and they don't know it's illegal. They are already not the smartest people on earth, as they work for free to a for profit company...

I think Google's fault is mostly just not enforcing copyright laws. I've never seen something on gmaps copied from osm, but I reverted a lot of changesets because they copied from google. So your experiences are not as general as you think