Majority? Where's your proof? I think "majority" is just conjecture... show me some numbers and I'll believe you.
Let me go do my homework and get back to you on that to see if it is the same across a larger sample.
If someone started at version 4 and they've kept current all the way through to version 7 then that would be the kind of stuff we're looking for.
After all, the point I was trying to make was that it is very hard for people to upgrade across major versions, so plenty of them are stuck with whatever was 'hot' when they first started out.
The knowledge required for migrating drupal to a higher level version is a lot more involved than for building the website in the first place.