Why use free math worksheets? Easy. These worksheets can save you a lot of time and money and when you're a busy homeschool mom teaching several children, this means a lot.
Even the youngest students--kindergarteners--will benefit from printable worksheets. They will help your little one learn and master basic concepts in way that will capture and hold their attention. Remember that small kids enjoy doing things rather than simply reading or listening.
Or you can usually find textbooks and workbooks at the public library, where you can also copy any worksheets that you want to use.
As a middle-school math teacher, I have seen many students who do understand abstract concepts, and even enjoy learning about things like Pi and the Pythagorean Theorem, but who appear to be unable to do so due to a weak grasp of math fundamentals.