We don’t give to receive, but that’s how human nature works, as pointed out by Shane Parrish at Farnum Street.

I think people are afraid. They don’t recognize the power of this rule. And they’re afraid that by going first and giving resources, giving time, giving attention, giving samples, and so on, they might just be losing that. They’re not cognizant of the fact that there’s such a strong rule in every human culture that says you must not take without giving in return.

— Robert Cialdini