He's wrong, tip whatever you're comfortable tipping. It's your money, spend it how you want. Reap the social consequences.
Full disclosure: I tip 20% or more 99% of the time. I tip 20% mostly because it's fucking easier math.
You can make some nice cash but as a former server I would have taken a guaranteed wage and benefits any day over whether or not it was a busy or slow week determining my income.
I go either way on that. I, personally, liked the hospitality business because it was good hard work for ~4 hours, but the harder I worked, the more money I made usually... and I made much more in 4 hours than I could have in another line of work for someone with little to know experience, like retail. Even working at crappy chains, I'd bring home $150-$200 on a Thurs/Fri/Sat night usually working 4-6 hours a night, but only working *hard* for 2-3 hours of that night... And this was in the early 2000s when i was 18, so it was a good amount of money for a relatively small amount of hours of work. It was a good fit for a young person in high school/college, IMO.
Of course, there were nights where I'd be "at work" and only bring home $50 or $60 too, but they were less often and I never felt like i was working hard those nights. If the norm was $50 or whatever then I wouldn'thave stuck around, the norm for me was usually much better than that... It would have been tough to earn that, in that period of time, in another line of work like retail or w/e, where I'd be lucky to make $7/hr back in the early 2000s.
As a teen/early 20s, going to college, I liked the restaurant industry. It's high stress though, hungry people are fucking assholes. And a lot of the people in the industry long term are fuckin dirtbags. No offense to those in the hospitality industry who aren't dirt bags, but FFS, a lot of your colleagues are dirtbags.
