They have not fixed it for almost 3 years - except for a really really tiny attribution only in web that too almost invisible. I challenge you to find it.
They've fixed it in the web, mobile will be fixed in the new release according to the linked comment. Maybe threaten to sue them if this is a priority for you.
Trivial - it's in the bottom right corner. It's easy to find if you're looking for it. The text is very small and has a bit less contrast than the one on Google Maps.