My personal experience is that 99.9% of people do their best to maintain honesty and integrity and although the vast majority suceed the disruption caused by the minority is way out of proportion to the size of the minority.
I can't argue with your personal experience. You must be pretty lucky if your statement is accurate. IMO I think we are fortunate if 80% of people "do their best to maintain honesty and integrity". I do feel most people are honest, but I stop in saying that all honest people do their best. Even the most ethical people slip at times.
An analogy I use is you receive too much change back at the local superstore. The superstore everyone seems to criticize for only selling Chineese products. Do you return it if you notice at the register? In the parking lot at your car? On the way home? Once you get home? What if it is a penny? Dollar? Ten dollars?
Ask a group of those people you think do their best, and I guarantee you the answers will vary.
I read a story on the Internet once about a guy that bought a wood working power tool at a show, that normally costs around $600. He got a discount of maybe $100-$200. When it was loaded up, he drove home, and discovered they gave him the wrong one - a model that normally cost $900. He lived hundreds of miles away. He called, they wanted him to return it and pick up what he should have got. Responses varied, some said they wouldn't have said anything, others said he should drive back on his own dime, most were somewhere in the middle and suggested negotiating something fair for both parties.
I think it is naive for any of us to believe everyone else has the same values as we do as individuals. Most people may be close, but there is enough variance that it can be risky to assign unearned trust to others.