I always get puzzled at how some people get indignant when there isn't a "Thank you" for a minor act of courtesy or kindness, either by themselves or by a companion. It takes the bloom off the act somehow, if there's a sense that it's done with the expectation of a payback - it turns it into a transaction.

"Thank you" is pleasant, and very welcome, of course - but it should be seen andnreceived as another random act of courtesy, not as a payment. The way you pay back acts of kindness is by being komd to someone else next time you get a chance.