Yeah but the Catholics never changed their scripture. The Friday fish was never based on scripture. It was just a tradtion.
I don't know if the Mormon hot drink rule is based on their scripture or not. But the "eternal covenant of polygamy" is in their scriptures. And it is worthy of ridicule.
The Friday fast (only one main meal a day and two light meals that do not equal another main meal) and the abstinence are ways of honoring the death of Christ on the Cross.
We choose our way for a purpose.