There are many, many social customs that confuse the hell out of me, but one of the most strange is the insistence of adults to pay for each others’ meals. In the US, when I would go out to eat with my coworkers, we’d always split the bill among everyone. Each person would pull out their credit card, and the waiter or waitress would give us each individual bills. Simple and fair.
In Spain, however, there is a big “buying rounds” culture that was very foreign to me at first. While this somewhat extends to meals, in Spain the “no, let me pay!” issue comes up more often with buying rounds of drinks. Due to the geographical layout of towns and the prevalence of bars, there is a big bar-hopping culture. So it’s very common to visit several bars on a midday walk with your friends, and in each bar, only one person in the group pays for the drinks. It rotates at each bar, and if you go an outing or two without paying for any rounds, people notice. I’m fine with this. The drinks are so cheap and the company so good that I rather enjoy it. You pay for a round, and then it feels, emotionally, that you get a bunch of “free” drinks after that.
What I don’t get is when people get insistent, or even angry, about the right to pay. This is not unique to Spaniards. Americans do this too, but mostly over whole meals, which is even stupider.