This is a good point. Though what CJ says about actions already reflecting the data seems to be a pretty reasonable observation. Perhaps people don't notice the data, perhaps their actions and behaviours arise purley through social mobility and memetic evolution.

Take for example the upper middle class and compare their stated ideals with their actual lifestyles on say divorce and other issues. It is hard to miss that they often behave as if they only had belief in belief but organized their actual lives by a different model. Someone being slightly cynical migh call this class warfare or perhaps handicap signaling.

But there might be a different better explanation. If say a society promotes ideals that make it harder for people to stay in a certain socioeconomic neiche, the behaviour of people that remain in that neiche will still on average be pretty decently adapted to it (or at least more dapted to it than anyone else) even if they state, belive and truly aren't using the now low status principles to organize their lives. You don't always need the human brain to come up with rationalizations, Azathoth can do it for you!

This is where I do think something like the handicap principle comes back into play. Evolution's beneficiaries are perhaps the people who in far mode most distain the rational self interested reasons or the easiest to grok rationalizations which recommend the course of action that actually keeps them in their neiche. Everyone notices what kind of people tend to have what kind of beliefs. Stabilising competence signaling ensues.