There could be a good reason for this. Take a look at the node on Multiple intelligences. Let's assume for a moment that this is correct, and all people are born with unchangable measures of the different intelligences. Everyone has different strengths and weaknesses.
People will polarize towards the jobs they are good at. If you are born with amazing computer skills, you are likely to get a computer-related job. If you have an amazing ability to play football, you may well end up playing a lot of football.
Now, most people aren't going to want to spend the rest of their lives worrying about their inadequacy in certain areas. Thus they will tell themselves that their skills are important. After all, they (the skills) got them (the person) where they are today. They may disregard other skills, rather like PC gamers who don't own consoles will rarely say that yes, a console is overall a superior platform.
Anyway, here's my point: People often judge other people's intelligence in the same category at their own, and vice-versa.
For example, I think my skills (programming) are better than some other guy's (memorising the winners of the last 25 years' Boulton Wanderers games), because I've been just fine up until now without knowing what he knows. But I've used *my* skills a lot.
I am confidently above average in the programming league, because most people can't program. I'm right at the bottom of the Accounting Skills league. I class myself as above-average, because I'm an above-average programmer.
In conclusion: Different people are value different things. By my own standards, I am above average. By yours, I could be really dumb.
Update!
I recently found the Journal of Personality and Social Psychology printed a paper in 1999, brilliantly entitled "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments".
To summarise: People tend to hold overly favorable views of their abilities in many social and intellectual domains. The authors suggest that this overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.
It's availiable online: http://www.apa.org/journals/psp/psp7761121.html
wick says The paper you cite won a 2000 Ig Nobel prize. You should add that tidbit to your w/u
WonkoTheSane says I agree with your overall point, but I think it is arguable if one is born 'with computer skills', or even with the ability to play football. Football skill(z) can be attributed to a combination of strength, speed, body mass, hand-eye coordination, vision, and, possibly, a little bit of drugs. And practice. Computer programming: logic, practice, patience, practice...I think you get the idea.
Mike1024 says Yeah... When I say 'born with' I kinda mean it as a blanket term covering both nature and nurture... that by a certain age, you tend towards certain skills more than others. If you've had access to a computer from a young age, you will be better with computers, etc. I think.