If something seems just stupid, it is always a good idea to try to understand the change. This one wasn't really voluntarily [1] (Though I agree for some recent changes, it seems impossible to find a reasonable explanation :/ )
Google is religiously avoiding doing things that don't scale. Just like hiring people to do customer support for their products, paying content providers doesn't scale.
Why bother paying Getty if it means you'll have to pay other people when they eventually sue you too. That just means you'll incur more an more expenses as people sue/threaten you. Far cheaper to just forgo the grounds for being sued altogether.
DuckDuckGo still has the functionality, but I don't think they pay content providers. From that I conclude that it's not just a function of "willing to pay vs not", but that "got sued" also plays a role.
Content providers in this case is every web page that is indexed for image search. Microsoft might have contracts in place with image services (getty, alamy, and whatnot), but I have my doubts that they pay every photographer's blog who's images they display in their image search.
More likely the other haven't just lost in litigation like Google has. The same group or someone similar may turn their attention to Bing, DDG, and others, now that this first case has completed in their favour. Unless of course the traffic through other search engines is not deemed significant enough to warrant the lawyer's expensive time, though the first case having been won will presumably reduce the potential costs of future cases (or make the search providers capitulate to "please turn this off voluntarily or..." without the need for even that effort).
[1] https://news.ycombinator.com/item?id=16388833