It might be in their interests to change, but that doesn’t mean they’ll do it. People can act against their interests all the time, especially when religious belief is in the mix.
Take a look at the history of the Catholic Apostolic Church. They were a group in the nineteenth century who believed the second coming was imminent and appointed a new set of apostles accordingly. Priests in the religion could only be appointed by those apostles. It was a fairly successful religious movement, but the years wore on and some of the apostles died. What would they do? They couldn’t appoint new apostles according to their dogma, so they carried on with the remaining apostles. More of the apostles died until there were few left. Surely they would revise the dogma now. No, they carried on until there were no apostles left. Because there were no apostles left, no new priests could be appointed. In turn, the priests became fewer and fewer in number. Surely they would change the dogma now, either appoint new apostles, or else change the rule that only apostles could appoint priests. No, they wouldn’t do it. The final priests died in the 20th century, the membership declined and churches closed. It was successful movement in the nineteenth century with many wealthy members and, despite its membership drying up completely, a legacy fund and trustees maintain their former church in London. The church building is now used by other groups. The building is testimony to a religion that died out rather than alter its dogma.
