I notice among people I talk to more enthusiasm toward learning French than Spanish. This confuses me; my feeling is that Spanish unlocks far more countries and speakers than French does and so is a more natural first choice.

What do people think motivates this choice?

French culture is still far more dominant, especially in the supposedly higher echelon, than Spanish culture. For consumption you have LVMH vs. Zara. For intellectually curious people, you have a lot of highly influential French thinkers in the past few centuries...