I think Google has experimented in the past with releasing things under separate brands, but it leads to the problem where if you don't mention the host company prominently enough users feel tricked (like all the people who use Instagram without realizing it's just a reskin of Facebook), while if you do mention the host company prominently you fall back into the same trap of user expectation.

Google also has the related problem where if they release even a genuinely uninteresting app (say a grocery shopping list) they'll still have a hundred million people try it out on the first day, so when building the app you have to build for that scale before you're even able to validate the design space. (There was one experiment, I can't remember which right now, which had a small team with didn't do this and then was widely mocked for being slow with "Google can't even make its own apps scale".) Damned if you do, damned if you don't. ...but I imagine the execs wipe their tears away with wads of hundred dollar bills.