99% of users don't even know they're being protected. There's no promise except "we work to make browsing safer" and cutting even 5% of malicious sites from a user's experience is an unmitigated win for that user at the low false positive rate Safe Browsing offers.
If the other options would just straight up kill innocent bystanders (e.g. false positives for legit shops) I think that is a tradeoff I am willing to make.