I teach Sanskrit which falls in this category (a religious / cultural / historical language). People show up to the class super excited to learn the language. They badly want to learn the language but have no clue how much effort it is to learn a new language. Learning the language is at the bottom of their priority list. You are not gonna be learning the language if it is the tenth item on your priority list no matter how much you "want to learn it". The semester starts with 20 people and by the end there's less than 10.