I think more people are aware that VCs raise commitments for a fund that they can pull in via capital calls than are aware that startup funding from VCs come with hurdles to clear.

This is perhaps because the most common round to raise is a small/early one, and these tend not to have hurdles. Founders that only ever raised these rounds wouldn't necessarily know what happens in later/bigger rounds.

Also, I wonder if capital calls come with hurdles as well? That is, can an LP refuse to put in more money if the VC's recent investments have not done well? I would think not, since it typically takes many years to determine whether investments were good or not.