There is evidence correlating being attractive to getting better tips, interestingly.

Anecdata, but I go to Taco Bell way more often than I should. There’s no tipping culture at Taco Bell, but the staff, at least at the one near my house, are always very nice to me and as far as I can tell my food is made with a sufficient amount of care.

When I do go to a restaurant that has tipping, people are usually nice to me as well, but I don’t feel like they’re really any nicer or better at their job than my local Taco Bell workers.

No, they're definitely more attentive for the tip, I just don't like it. If they're going to be extra nice, I don't want it to be for money. Felt nice going to other countries like Australia where the customer isn't always right but they still do their jobs.

Anyone who has worked in a restaurant or bar can provide plenty of observational data that if you provide better service you will be tipped better. I would recommend trying out working as a server/bartender you will understand tipping a lot better.

There is definitely a huge difference in countries where they tip and countries where they don't tip.