Maybe I was unclear. Technically set theory is a branch of logic - I found that very useful to understand when I was studying discrete mathematics, and later when I was trying to understand the relational database model.

Yes, most of math is intertwined, however in the examples given above its just useful (at least in my mind) to know the how set theory fits into the larger branch of logic.

It appears that folks are seeing an attack/criticism in my post, probably because it was fairly succinct. Nothing could be further from the truth actually, the list I responded to is quite insightful - and I upvoted it!