I agree with your point about the funding process being oversimplified. However, I've seen many founders become emotionally attached to their MVP, convinced it's good enough to scale without fundamental rethinking.
They push forward with what's essentially a throwaway prototype instead of rebuilding it properly with lessons learned from initial user feedback. And some people are just cheap by nature. Last point is a huge one, even when funding is good enough. Does not make sense to make, I've seen it.