When there is little or no good competition, people providing a service tend to have less incentive to do a good, pleasant job. Or, as Scott Sumner says,
... government offices don't have to compete for customers as private companies do, so they don't care very much about customer relations. Of course some private monopolies suffer from the same problem.
Of course his statement is provocatively strong, but in general he is right. Petty bureaucrats can get all officious when dealing with us if their bosses don't much care, and their bosses will tend to care less if we customers have few, if any, good options.
Yes, some gubmnt employees provide great service. In fact we had a very pleasant experience last week at the passport office, renewing our passports.*
And with increasing competition from private couriers, we have noticed that the postal service is slowly improving the quality of its service, at least in areas where the competition matters.
Harold Demsetz frequently argued, the major source of lasting monopoly power is gubmnt. Whether the monopoly is gubmnt activity or gubmnt-created or gubmnt-protected monopoly, it is in these types of monopolies where people tend to have less incentive to provide good customer service.
And, after all, people respond to incentives.
Note: I said "tend". I know there are dedicated people who work hard to provide good service in gubmnt or other monopolies.
*Digression: We took a gamble and renewed our passports for ten years. When I laughed about that, the passport official said someone who is 100 years old had recently renewed their passport for ten years! Heck, I'm still <90.