You Chrome folks need extensions to use non-Google search engines?
Firefox uses just bog standard OpenSearch definitions. No shenanigans. Ships with both Google and Bing if you're into that sort of things. And you can add arbitrary search URLs, no probalo.
A lot of e-companies, particularly the search engines, around the turn of the millennium, went completely crazy over the "portal" business. Everyone wanted you to make them your home page. News feeds, generous 15 megabytes of email space, web search index last updated 1.5 geological megacycles ago - "well, you see, the web sure is growing rapidly, dunno if anyone can do anything about that in the future, we sure can't". Oh and ads. Lots of ads.
So in that light, Google kind of stood out. Actually updated search index, relevant results, no-nonsense user interface.