I think it started when I was in a congregation that had very little territory that could be worked on the weekends (there were a lot of businesses that were closed on the weekends). We would "stretch" the field service time by walking slowly, taking long breaks, etc. I finally started questioning (my bad attitude I guess) the rationality of wasting 2 hours or longer when we could have done the same amount of preaching in a half hour and then go home.
I couldn't believe that a person who wastes time between doors is in some way more pleasing to God than someone who wants to get things done in a timely manner. Looking at it objectively, it's all about control.