Department of Motor Vehicles? Why do the workers there seem so disgruntled? Because of time asymmetry. The amount of time you have and will invest in taking care of your errands at the DMV is orders of magnitude more than the amount of time a worker will invest in handling your matters.
You only have one appointment, whereas any given worker may go through dozens of customers in the span of a day. This imbalance and asymmetry is what leads to conflicting attitudes towards the same interaction between the representative and the customer, and why both sides seem to loathe the experience.