Cultural practices become ingrained, and people soon come to believe that what they're used to is "right" and that anything else would be "wrong"
Many people don't eat pork, even in cool European countries with scrupulous hygiene, meat chillers and well-equipped kitchens, due to what used to be sensible practice in hot, middle-eastern areas with poor sanitation.
Many people, especially in US, practice male circumcision, even though they have ample access to washing facilities and good treatment for infections. The practice would be more useful if they lived in tropical or hot dry desert areas.
Some religionists are forbidden to marry or have sexual relations with long-term adult partners, and end up with some very abnormal behaviour. The original reasons for this rule (preventing inheritance of wealth and privilege by the sons of Bishops) has long been forgotten.
There are still people who believe that it is intrinsically wrong to hold religious ceremonies in a language they understand, and it is "right" to hold them in an obscure and long-dead language.
Other religionist believe that they can only perform their duties if they are one gender but not the other.
I'm sure you can think of lots more examples.
Because we have given up burning witches and heretics, and it is no longer a crime to believe in transubstantiation, we like to think that European people are immune from irrational and damaging behaviour, but it isn't true. Even today a man can be beaten to death by people on their way home from a football match because, although he was a Christian, he was the "wrong sort" of Christian.
