I personally know dozens of people who got out of the restaurant/bar biz into "real" work purely on their effort and attitude that was noticed by customers.
You nailed it. When somebody provides me cheerful and competent service, I go out of my way to tip them well. People that can have fun and excel at a low-end job are destined for bigger and better things. Business owners would do well to notice these kind of ambitious go-getters and hire them away for their own business. Bet they’d have a higher success rate than the traditional resume/interview process.