Google's motto "Don't be evil" is not rigorous. Huawei claims something similar recently. The problem is who defines what's good or evil? Every group of people think they are noble, and the enemies are evil.
Prospective Google employees saw what Google meant by "Don't be evil" by seeing how Google behaved (and specifically how other Google employees behaved) and decided it was worth following. They didn't just see the three words and think that sounds great.
And I disagree that every group of people thinks they're noble - the comment I replied to specifically says that companies are better when they do not see themselves as noble and only see themselves as profit-seeking.