A terrorist finds it much easier to execute on insidious plans if the world's information on vulnerabilities and weapons are organized at their fingertips, for example.
But you've sort of hit the nail on the head: there are consequences to building these things, and consequences to not doing that.
Up-thread is, I think, making the fine point that the bad can certainly outweigh the good (you'll note a distinct lack of "Google but for CSAM," at least outside the dark web, and that's I think because the good/harm tradeoff there is self-evident). My intent was just to put down a reminder counterweight that the good without the harm is likely also impossible.
Google makes errors of judgment. They also make straight-up unforced errors (breaking their 10-year commitment to the Chromebook platform, at their scale, is just burning credibility at a quantity that I cannot imagine is going to save them enough money to justify it unless their intent is to exit the educational space completely; 10 years isn't a random number, it's the kind of number that gives educational institutions the confidence that an investment in platform is long-term, and breaking that commitment factors into the calculus of those institutions trusting Google for any and all future purchases).