I was rewarded for being smart when I was a kid, which may not be the same thing as thinking.
I've known people who liked thinking and grew up in anti-intellectual environments-- they were very happy to get out.
I think you've got a partial truth there.
I had the same experience, but 'being smart' is an inherent feature of you, not a product of your work put in, so I felt insecure about possibly doing dumb things and damaging the perception of me as smart (which probably contributed to my adult issues with asking for help and fear of failure).
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?