Because a single source of income (Google) isn’t smart for anyone. And the more money is involved (in this case, a gazillion), the worse it is to do so. What if Google just one day decides to not renew their contract? Mozilla’ll be out a gazillion dollars a year.
That's a hypothetical scenario. I'm talking about the reality: Google was paying Mozilla close to a billion/year to be the default search agent. That is a shit-ton of money.
