I don't know many moms who can teach it either, but I also know hardly any people who need it.
For those students who want it or need it, there's online courses, community college, or taking the class when you start at a 4-year college.
Not everyone needs it. But it helps america keep a technological edge that a significant fraction CAN understand and use it. And lots of high-school age kids are capable of learning it. (One could argue that if home-schooled kids are so much better off than other students, they all ought to be able to learn advanced math as well as other advanced subjects). The same could be said for foreign languages (how many parents can speak more than one language?)--and foreign languages are easier learned when one is younger.
I'm not trying to bash homeschooling--parents who do this are obviously committed and serious about providing their kids with a good education. I just don't see it as a panacea. (I also think anti-intellectualism is as dangerous to the nation as the erosion of educational standards, but that's probably a better subject for a different thread).