Why do people do this to themselves?

Why do people do that? After reading some martial art postings on a forum, I have had to ask myself: Why do people try to compare themselves with others? This question has been rolling around in my brain since the first day that I started training in karate. What are the other people looking for? Are they thinking "Wow.. my punch is faster than hers?" BUT how do they know whether the other one is doing full speed or not. The other person could be holding back that day because they had injured their wrist earlier. How do they know whether or not their technique is proper as they throw this "fast" punch. It astounds me that people try to compare themselves with others. The fruits of this comparisson are only lies. One could be led to believe that they are extremely good at kata, but they may be feeling the "Big fish in a small pond" syndrome wherein all the other students are at a lower level than them. Once they get to train with a group of higher belts all of a sudden these people would feel like they are imbeciles, and incompetent at kata. Then we are walking on a strange path that makes us surge to the tops of mountains of negative self- pride feeling superior to others, and then fall down the cliffs of the reverse action which is putting oneself down with anger, and derision. Not good to our goal of training in karate, and not healthy for our mental selves. The only comparison we should be making is to look at ourselves and ask "Have I improved on those things that I'm working on?" If the answer is 'no" then we need to make a plan to improve exactly those things. If the answer is "yes" then we can make a plan to use this upward effort to improve something else. The fruits of this kind of comparison would be to gain in positive self-pride wherein we feel that we have accomplished something good in our lives.