You shouldn't drive too slowly because it annoys people.
Dennis comes through the highway on ramp, doing 20 mph and merges into the left lane of the highway where the limit is 65.
Dennis wants to decide what speed to speed up to.
Dennis decides to accelerate to 70 and keep it there for the time being.
Dennis decides to accelerate until he hits 25 and keep it there for the time being.
The driver behind Dennis is appreciative that Dennis is going as fast as he can, as 5 over is basically the defacto legal limit.
The driver behind Dennis is angry that Dennis is going 40 mph under the limit and doing so in the passing lane.