Maybe for a long time butter was the only form of dairy that adults could enjoy without lactose intolerance.
I don’t know, I just looked it up online as Origin of Butter, and that is what came up. I know in Bible pork was unclean and not used in Old Testament, but was declared clean in New. Probably had to do with smoking/processing that came later.
Butter is versatile, and improves flavor of lots of things. It is great tenderizer/marinade for steak. I never liked margarine, it was a fake food...refused it.