While going through the Haskell literature I uncovered a passage that said that, I'm paraphrasing: Complexity was at a premium. The task was very complex and what was needed to get Haskell to achieve its goals was extraordinary. This might explain how laziness kept Haskell pure. Everything was at a premium and this developed a discipline to keep everything streamlined. This suggests that purity had a material benefit, but the problem is it is conceivable that its material benefit was merely psychological. I do not have enough time to study what Stephen wrote at the moment so I will need to revisit it. He cited some references.