In Australia it's customary to thank the staff members attending your table. So when they top up your water, or lay out cutlery for the next course, or clear plates, you say 'thanks/thank you'. Same for people clearing glasses in bars. It's like a millisecond pause in your conversation to thank the staff member; it's basically cell memory, you don't think about it. They may or may not acknowledge it with a smile or 'you're welcome/no worries'. . It's just a basic manners thing.

I and my partner were doing it in the states and it was clearly unnerving the staff. Lots of puzzled looks or 'thats ok hun' like they had to reassure me that it was part of the service.

Do people just ignore staff there? Is paying a tip at the end the only acknowledgment that they exist?