It depends on what you need to search for. i use DuckDuckGo often... but when I'm searching for some things I can get different results or more results if using Google. They do have more advanced search algorithms, as well as having indexed far mor websites I would think. And if I need to hire a contractor or business in my area... a lot of businesses use Google adwords... so if, for example, I search for "electrician in Seattle'... their ads will pop up. It's helpful sometimes.
And unfortunately for me I'm old enough to still remember when Google wasn't around, and I used some of the other popular search engines some people above referenced. I still remember someone telling a group of us to try this new thing called 'Google.' For a lot of people like me... using Google wasn't just a learned behavior as you suggest. We began using it out of preference. For younger generations perhaps it's as you say.
it's interesting because for a lot of businesses I don't have an issue with them becoming huge, due to being very good at their core business. It's when they start branching out and taking over everything they can, due to that size. Amazon is far more guilty of this. They completely took over selling stuff online... but then started owning a lot of other websites, starting movie productions, taking over the post office in effect, etc.