The tipping culture in Spain seems to account for this acceptably well. 1-2€ left on the table for a staff member who poured you a couple of drinks seems to be generally well received. Of course, they know a table of American tourists is likely to be a gold mine so far as tips are concerned.

In the UK tipping is very hit or miss. Especially now that cash payments are becoming rare. I've noticed that food delivery drivers will be half way down the street by the time I open the door these days. They obviously don't expect anything. If there is a service charge on the bill I typically don't leave anything in particular, and I'd prefer it this way.