I think it is a side effect of what keeps google from turning into IBM. Ossification is a perennial problem for large corporations especially traditional growth companies. They make their few big things then iterate on them. The "ADHD" shown by google, while it is annoying to users to have a perfectly serviceable piece of software discontinued unceremoniously, probably keeps the internal structure from becoming rigid and failing to adapt. I think they are probably slightly too far over on the side of kill stuff and move on but I'm not a multibillion dollar company.