Why Do I Need a Math Curriculum

Really? I'm not bad at math - I don't fear it (I'm starting to fear phonics, but thats another post). I'm looking at MEP, and I was reading about Mammoth Math. I just don't think I need a curriculum to teach addition and subtraction. (Yes I was also reading livingmath.net - playing War by adding two cards is a great idea.) I'm not going to teach Algebra on my own, but on the other hand, my brother picked up math FAST when he started doing woodwork. He had a reason to use it.

My son likes filling out workbook pages, but I could get those fairly cheap (or free online), or even make my own. I already have some Kumon books for him - the telling time and I'll get him the counting money one later if I think he needs it.

I guess what's the point of math? Spiral vs. mastery, manipulatives vs. workbooks. If I think about the end goal I want him to take enough math to get into college (or a tradeschool / field / whatever). I also want him to be able to USE math in everyday life - to see its application. Perhaps not love math, but at least appreciate its value.

I want to have more fun I guess - he likes to learn, especially math, and I don't want to ruin that.