That makes sense; most people can tell if you're just making conversation in order to suck up to someone vs. are genuinely interested in talking to them. So if you genuinely do care about a person and show that through your interaction with them, they'd be likely to appreciate it more, and show that appreciation.

I'm curious, though: if you have nothing to say to a person, and don't say anything, do you get more or less of a tip than if you were to (insincerely) attempt to make polite conversation?