@Mismo
@Radaketor
Yeah sometimes I forget about the cultural differences in other countries vs. America. You're both quite right in that it is a cultural thing and also sometimes I forget which users are/aren't American, with a general (sometimes false) assumption that they're American. So that's definitely "my bad". I think it's because when there aren't any blatant foreign errors in someone's English, it's quite easy to assume they're either American or British but Brits tend to give themselves away by their word choice. So if anything it's a testament to your excellent English skills.
So in each of your countries, tipping may not be as customary as it is in the US. So if it isn't something people generally do then you're definitely in the clear. But if you're a non-tipper in the US you'll definitely make a lot of enemies. The problem is that most restaurant workers are not even paid minimum wage and must supplement their income with tips and while technically if they don't make enough in tips to make minimum wage, the restaurant owner is supposed to cover it, in actuality what happens is if they ever complain to the restaurant owner about not making enough in tips they instantly get fired, or if they complain about it too often.
It's ironic because the "minimum wage" isn't really the minimum wage. It's only the minimum wage for certain kinds of jobs. For restaurant workers, they might only get like $2.13 an hour (where the minimum wage is like $7.25 an hour), and they're expected to "make it up" in tips. So when tips should really be a something extra for when someone goes "above and beyond", in America it's a part of someone's regular pay.
So if you're regularly not tipping those $2 workers they're going to get pissed at you really quickly and pissing off a bunch of poor people isn't really a good idea unless you don't intend to show your face around those parts again, because they will remember. It's not just one restaurant or a few of them either -- they're practically all like that, outside of maybe the very most expensive restaurants where a typical one person meal is over $100 or something. I can't imagine the people who work there are working for less than minimum wage. They'll still get pissed at you for a non-tip though.