>>11926045Cause functions are a very general sort of relation which still offer a lot of structure. Orders are similar. In math, we usually want to study things which are specific enough to have some properties but which are simultaneously general enough to capture a lot of behaviors. It's always a tug of war between these two, and people with different levels of generality. But functions are one of those things which strike the perfect balance.
I mentioned orders, and there's also equivalence relations. All of these types of relations show up just about everywhere, so they're studied in detail. Other sorts of relations don't really show up very often.
