[Nasrudith]

It is because people just stick with their best usually instead of using a variety of search engines. It becomes rather winner takes all.

Google for general search. Duckduckgo fir general if you want something a bit more private but not extreme enough to run your own spiders. Bing mostly for porn search - not being snarky some people do consider it to have better results.

[beatgammit]

And searx.me if you want to be even more private, and you can run that yourself if you so choose.