They aren't interchangeable. "i.e." is equivalent to "in other words". "e.g." is "for example".

The distinction matters because i.e. implies English is the only non-phonetic language in existence.

> I think in casual speech at this point (at least in my experience) the two are used interchangeably.

How?

They don't mean the same thing.

Well, the thing is… when you use a borrowed term from a dead language, in writing, it really sounds wrong to cultivated ears. I really had to double-check that sentence to see if I had parsed it wrongly. Not bragging, just saying.

They cannot be completely interchangeable:

“There are white people among us: i.e. me and my father” is totally different from “…: e.g. me and my father”.