The thesis of laziness by default isn't "everything should be lazy", just that there's some benefit to having strictness be something you add as necessary - maybe that it's easier to add strictness to something lazy than add laziness to something strict, that it gives you more abstraction power, or maybe increases surface area for optimizations.

Similarly, the existence of generators and zero-argument functions in Python doesn't undermine the idea that strictness by default could have benefits.