Because of ideological reproduction (educational systems, media and political discourses) which all normalize capitalist (and materialist, dualist, etc.) worldviews. There's a lot at stake in defending this as it is the basis of people's identity and how they construe meaning in life (through work, career, status, consumption). Colonialism has also been an effective project in destroying other worldviews and political systems and labeling them as primitive, backwards, etc.