Just learned that a friend of mine always tips 10% on takeout. Ive never tipped on takeout unless they offered me a water/soda while I waited or something.
US biased, but I’m a little curious about other countries as well.
It's a question of opportunity cost. In order to be really attentive they work fewer tables, so they need to have higher margins to make up for lack of volume. If you can't afford a 15% tip, or 20% for good service, you shouldn't be eating at an expensive restaurant to begin with. That's the social compact in America, that's how it works. Until servers start being paid a living wage, you're not the arbiter of what constitutes paying "enough", you're just rejecting cultural norms and hurting servers so you can save a few bucks.