Culture is maintained by being inherited. That happens through cultural inheritance proper (e.g. social learning, teaching, being exposed to local language, norms, practices etc) in combination with biological and "geographical" inheritance.

It gets its grip on the humand mind by becoming embodied from early on in development. Later in life it is continually fortified by constant exposure.

My point is that culture is just as much of a deterministic bitch as anything else. People believe that many traits, including intelligence and personality, are determined by genes, thinking that the outcomes are much less malleable than anything culture can do. But that's wrong. Whatever mistress you pick, biologgy or culture, there's not much to choose between them.

(Spoiler: in reality, biology, culture and environment always co-determine the phenotype, so pitting one against the other(s) has always been an error.)