I'm not the parent so I can't answer from their experience, but I will say that laziness in Haskell lets you write functions that cannot be expressed in Lisp without macros.

Some simple examples are when and unless, which work like if...then and if not... then.

In most languages, these would be control flow statements built into the language (or not) and could not be written by the user. In Lisp you could implement these with macros, with all of the caveats that apply. In Haskell they're just ordinary functions with all of the benefits of being first class values at runtime.