but I'm not sure what the general difference is between me and most people, or Yvain and me.
I think you should differentiate between intellectual drive and productive drive. Yvain happens to have both.
Intellectual productiveness takes a lot more effort than intellectual consumerism. Surrounding yourself with people who happen to appreciate your intellectual products rewards both intellectual and productive drive. You have to exceed a certain threshold of production before you will get sufficient motivation from those social rewards, though.
One of the big variations I see between people is the amount of energy they habitually put into thinking, and I haven't seen this discussed anywhere.
General advice about improving health and lowering intellectual friction would seem to help increase the ability to think, and ideas like "take five minutes to consider the problem" adds impetus, but I'm not sure what the general difference is between me and most people, or Yvain and me.
Intellectual drive isn't an unalloyed good-- cranks have high drive combined with low self-editinig, and some types of depression include a compulsion to think about topics that cause misery and/or inertia. Part (all?) of the value of meditation is getting some time off from thinking. Still, increasing intellectual drive would probably be a good thing for a lot of people.
Has anyone found that rationality training or anything else increases the default desire to think?