A major challenge of alternative
#search engines seems to be that they have to be *reliable* in the sense that they should work, always.
Web search is an essential tool and if it's not available or quality noticeably degrades (hard to monitor!), that's a major headache for users.
One can argue that you can temporarily go to a different engine, but you have a preferred engine for good reasons (e.g. customizations, UI, etc.). When you have a car you like and used to you probably will struggle even with a very good replacement you got while yours is at the shop.
@kagihq