Absence of evidence has never stopped schollars from making stuff up whenever it suited them.
Chomsky held that each child must be born with a language acquisition device, usually shortened to LAD (some linguists, terrified of looking sexist, suggested instead a language acquisition support system – LASS!).
When you`re trained to see things a certain way, it`s amazing how blind you can be to the obvious. To really get to the heart of something, you can`t have too little training.
The downside of higher education is that it gives you the confidence to maintain baseless fantasies in defiance of common sense.
One of the differences between linguists and people is that people like words better than grammar and linguists like grammar better than words – they`re looking for systems, and words just aren`t systematic.
This last one is not quite true (I`m a linguist, and I like words better than grammar), still notable.
Please don`t let the Quotes above mislead you! The book does treat language, with samples and examples.