Why is calculation not considered for sighting the crescent of Ramadan, but is considered for prayer?

Question : Shaykh, may Allah reward you. Why is calculation not considered for sighting the moon in the countries, just as it is considered in the old wars?

Answer : This is not a matter of will; will is based on the Shari'ah texts. As for practice, we know what we know. Ask those who divided it up; you are the one who gives the answer. He says now: We rely on calculation for the times of prayer, so why do we not rely on it for the times of fasting? I say: This does not need an answer, because this is a contradiction in practice. So ask the one who did that?