Google censors information relating to that 10% for everyone else. They don't care enough to switch.
Centralization is an issue _a priori_. It's giving power to a single entity that we have no reason to trust will act in everyone's best interests.
Google Search is a consumer focused product, if they don't serve up the stuff that the users want - they loose viewers. No viewers - no revenue. Their bottom line depends on giving each person the best search results possible.
Pretending that they'll just decide to cut off even 1% of users is insane.
If they can make 2% more by selling out half their users and giving them inferior results to serve the interests of somebody or something willing to pay Google money to screw over the users, they will do that without an instant of hesitation, in the absence of oversight. They are in an absence of oversight.
You are wildly in error to believe that people magically can tell they're not being harmed. People absolutely have no idea whether they are being 'given the best' anything possible, much less something like search results (or information in general).
It is highly profitable to screw over mass audiences for one's own benefit and there's largely no mechanism to prevent this… again, in the absence of oversight.
The most annoying bit is that it's never the majority. It's at best plurality that "gets" to decide.