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?

Being a French guy in the US (east coast) for 10 years married to a Mexican wife, I am still amazed by how much people here love (or at least "react positively") when I speak french 😅  (and I see that often because I only speak French to my kids). 

My guess is that spanish feels more like an "utilitarian" language?