I'd say they definitely are, to people studying the subject matter; it's hard to find a sociological analysis of contemporary capitalism (in terms of culture, alienation, fetishism or otherwise) in the literature that doesn't at least mention critical theorists, and it's hard to find studies on political deliberation that don't mention Habermas. The point is that if Scott were to engage in such literature, he'd have to address some of the claims anyway.

Not being part of Scott's audience (and therefore he should have no concern with mentioning their work which is often highly relevant to the topics he writes about) seems to just speak in favour of an echo chamber rather than considering and criticizing ideas that are already out there and hold sway with people informed on the topics.