That's a question that cannot be answered without looking at math major's area of focus or their specific career of choice, of which I am ignorant about.

That being said, I don't think a math major or a person who is in a strong math related field necessary focus on everything that requires high school mathematics. They may not touch statistics, or linear algebra as often as other area because they don't need it in their day to day job. They may need khanacademy to reviews those area that they didn't touch.

In a highly technical field like programming, most programmers may not need to deal anything more complicated than algebra, so they're going to forget the more advanced aspects.