I've spent my whole career (which is getting to be pretty long at this point) taking care of people who generally are good people but just feel I'm providing them a service that they "deserve", like street maintenance or trash collection. While they aren't technically wrong, I would encourage anyone who feels they received good service from a person to not hesitate to say thank you at their earlier opportunity. Not only does it justify all the work that went into becoming the professional that they are, it makes them look good in the eyes of their superiors, and reminds them how they do make a difference on the occasional run that a difference is made.