My understanding is that you get promoted at Google for launching new things, not for maintaining them, so there's a perverse incentive to launch projects that become orphans almost immediately. So much so that I wouldn't even say that they retire popular services prematurely, but that because there is no institutional will nor support for these projects to survive into the future, they are simply de-launching proofs of concepts. Translation: nothing is intended to survive at Google besides search and AdWords, and everything else is subject to cancellation at any moment without warning.
I'm not sure what you're saying about sharing blame, that these products are too popular? I'm not sure that's a sufficient reason, but it would certainly explain Google's overarching product strategy through the decades.