Mormons should not drink beverages high in caffeine and theophylline, and green tea contains large amounts of these substances. I don’t know exactly why they can’t consume caffeine like this, but I think it’s because it would make their lives easier, too, and it certainly doesn’t fit into their religion. They have a revelation of the so-called Word of Wisdom, which they follow faithfully, in which the consumption of fruit or herbal tea is allowed to them.