Perfunctory means done as part of a routine or duty. If you give someone a gift and they look at it like it's roadkill and say nothing about it but a perfunctory "thank you," you might not be giving them another one anytime soon.
A person who does something in a perfunctory way shows little enthusiasm or interest in what they are doing. Many of our everyday greetings are perfunctory. For example, when we say hello and how are you, it's usually done out of habit. Perfunctory is from Latin perfunctus, from perfungi "to get through with, perform," formed from the Latin prefix per- "completely" plus fungi "to perform."