Money. Particularly adsense, which rounds to the idiots at google incentivizing / putting lots of the dollars in that fund seo, effectively incentivizing and funding the ruin of their own search engine. I think they were arrogant enough to believe they could outwit the seo, but seo has pretty conclusively won. And a need to juice revenues for the stock value.

Try kagi. I was skeptical at first about the idea of a paid search engine, but my experience has been they are mostly simply better than google for all searches related to software development, and at worst, equal.