I had read someplace that this is why people made egg noodles, because they were able to dry the eggs once they were mixed in with the flour, and then when they cooked the noodles, they had more protein and vitamins in them than just plain pasta without eggs would have had.
I know diddly about butter. My wife used to get Kerrygold but found a Costco brand that she thinks is nearly identical for considerably less. https://www.allrecipes.com/article/costco-kerrygold-butter-knock-off/
Another reason for pasta I would think is that it can sit around forever and not spoil, but the ingredients separately would.