survival under capitalism pushes you to think of everything in terms of financial benefit

"On the basis of political economy itself, in its own words, we have shown that the worker sinks to the level of a commodity and becomes indeed the most wretched of commodities; that the wretchedness of the worker is in inverse proportion to the power and magnitude of his production"

People internalize this form of self worth and they cannot think outside the confines of capitalism.

Materialism, baby. Our thoughts on "human nature" are inevitably tied to the society you live in. Pre-capitalist peasants thought that the sun takes revenge on those who curse it, trees and rivers were conscious, and that plants and animals have secret knowledge. They were much more in tune with the natural world and the rhythm of the seasons by necessity. Capitalist ghouls can't imagine people doing something without it being an economic exchange of value.