Sorry, jumping in on this one a bit late, but thought I'd add my 2cents.
Simple math is useful on a daily basis for everything we do. Higher level math is very useful to some, but not all. Therefore, why do it? My response is that even if you don't need the mathematics portion of it, it teaches logic. Math is pure applied logic. It teaches you how to solve a problem in a systematic way, and apply a step-wise approach to problem solving.
I too help my daughter with 7th grade math, and am amazed at the level of work they are doing. I don't remember doing some of this stuff till I was in college. She (fortunatly) has a very logical and mathematical brain, so most of it comes fairly easy too her, but she still struggles at times. She gets very frustrated, and asks that impossible question: Why do I need to know this?
I struggle with the quantity of homework kids are getting these days. I worry that they are so immersed in homework that they don't get a chance to be a kid, and get outside and be active. I think a lot of socialization skills are lost this way. It is interesting to find a group of pre-teen/teens, and not one of them is talking to the group they are with, but their all on their cell phones talking/texting to someone else. I remember reading a study that came out of Sweden or someplace, where they tested 2 groups of kids. One group got the usual amount of homework, and the other got none. When they tested the two groups later on, their grades were essentially the same. Some argue it is a way to relieve the teachers from having to teach as much in class, while still cramming the same amount of information into their heads. I dunno if I agree with that assessment, but find it interesting.
Erik