Google co-founder Sergey Brin told public radio’s Marketplace that around one percent of all Google searches go through the "I’m Feeling Lucky" button. Because the button takes users directly to the top search result, Google doesn’t get to show search ads on one percent of all its searches. That costs the company around $110 million in annual revenue, according to Rapt’s Tom Chavez. So why does Google keep such a costly button around?
Take into account the number of people who’d switch to, say, Yahoo, being so disappointed that Google removed the "Feeling Lucky" button. Everything has an effect on making money — even making money. For a more clear example, let’s say Google would start showing a banner ad on their homepage from now on. Google would make loads of extra money, but many people might also use Google less, or start blacklisting the ads on Google via their ad blocker, and so on.
So, it makes sense to keep people feeling lucky.