The phrasing you use implies a conscious decision.

I think it is safe to say that when the issue comes up for consideration, most smart people make a conscious decision not to waste time improving their rationality. It may not be the best possible decision, but we rarely make the very best possible decision.

The idea that there is more in the world that is amazing and useful and worthwhile to learn is not particularly widespread.

I think many smart people continue to learn new things about the world. This doesn't generally translate into improving their rationality.