Google search requires a lot of resources to crawl, keep indices up to date, and provide user level significance (i.e. different results to different users). Then couple it with their other services (Google Maps, etc).
The competitors have not come even close to Google's level of quality.
With LLMs, it's different. Gemini/Claude are as good, for the most part. And users don't care that much either - most use the standard free ChatGPT, which likely is worse than many competitors' paid models.
It's not just the quality. The are people who do complain about how they perceive it significantly decreased over time. Yet there are many other factors, including presence as default search engine in so many setup out there.
Google was always terrified by the fact that they had no moat in Search. This was clear from interviews and articles at the time. That's why they decided to roll up the ad market instead, and once they had the advertisers Search became a self-fulfilling monopoly.
Google Search would be moatless if not for the AdMob purchase.
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