> $20M/year really is a waste of time for a $200B/year business.
That's the thing though, it isn't a waste of time.
One can hear very similar logic from people with investments. They will say "The stock market is returning X% / year and is way better than those bonds with only 3%/year. Investing in bonds is a waste of time."
They say that because they have yet to internalize the value of having a diversified their investments. Not everything goes up all the time.
It only makes sense for Google if the Search Ads business were to never ever lose its profitability. And yet, it is losing its profitability. As a result, Google has to aggressively cut back on expenses, remove projects, end of life products, etc as that cash cow slowly deflates.
Consider then the alternative where there are 10, 20, even 30 business lines within Google generating $10 - $30M of profit each. 30 businesses at $30M is only $900M, less than 5% of their revenue, but those businesses are SOLID and provide a supply of management talent, consistency, and some bucks to keep the lights on elsewhere.
That is diversification of execution risk. It works the same way investment diversification works, it adds other, less high margin, businesses to the portfolio that are all revenue positive.
A company like Google can use those businesses to experiment with alternate user support models, management schemes, policies, and communications. All of that helps the "main" company to mature in its thinking about how to be a business. Sadly, executives who have never had any experience other than one wildly successful business tend to think exactly like you do, "Why would I waste time on piddling little products when I've got more cash than I know what to do with being pumped out by my main business?"
Short answer: "Things change."