A reader puts it well:
Math is more about training your mind than equipping you with a tool for living. It's no secret that high school math is useless, but that doesn't mean it's pointless.
I suppose that you were trying to be provocative with a post like "Math is Useless". It's supposed to bring people like me (an applied math Phd student at a major university) out of the woodwork to talk about all the great things that math has done for modern society. This is, of course, all true. However, we have not derived such a great benefit from math because the majority of people are required to learn how to calculate the interior angles of a polygon, but rather because of the small minority (maybe 5%, probably less) who have continued to pursue math after high school (of their own accord) and ended up in a vaunted STEM careers.
If we want to talk about useless subjects, I think we have to recognize that math, as it is currently taught to American high school students, is just about as useless as Shakespeare that is being taught to these same students.
I suppose for a moment that mathematics is only useful "if you engineer planes" or something. When is the decision of whether a person will engineer planes to be made? Should I tell my kids who are in middle school, "Decide now whether you would like to engineer planes, this stuff is useless otherwise." Should this be decided in high school? Before college? By whom?
It should be noted that without a certain level of mathematical proficiency, about half of the available college majors are essentially eliminated for that student. Many Americans seem to be okay with that choice; students from many other countries are not. Even if one does not wish to spend their lives "engineering planes" an educated populace requires a certain level of numeracy. People rightfully worry about illiteracy; what about innumeracy? Should people be able to solve a simple equation? Understand the notion of compound interest? Percentages? Understand the exploding amount of "data" and "studies" being fed to them daily, especially on unscrupulous "news" sources?