I suspect that one of the main reasons is that people read it and think they have to adopt all of it.

Personally I still recommend it to people but with the caveat that they need to think about what aspects from it they adopt and which don't make sense for them in their environment. E.g. if function calls are expensive in the language they use and its compiler doesn't optimize their code by inline the ones it can, then they probably don't want to break things down to the level that Clean Code recommends.