Procedurally generated environments require very, very little storage space (you essentially need to store a few hundred seeds and parameters) and for most game

Procedurally generated environments require very, very little storage space (you essentially need to store a few hundred seeds and parameters) and for most games nowadays, storage is actually the biggest bottleneck of all (not just HDD but temporary buffered storage). Procedurally generated environments basically approach Kolmogorov-optimal compression for a given domain, without any loss of fidelity when done well. And the generation itself is usually not more computation than the polygon rendering.