Math is dirty. Math was created by businessmen who wanted to be monopolists. By gamblers who wanted to win, or at least to postpone the day when they would go broke. By scammers, and those who wanted defense against scammers. By people who wanted to blow up their enemies in war and who were moved by hatred and revenge. A recent mathematical construct born out of academia wants to destroy the US dollar and turn the world economy upside down. There are people trying to take over another planet with Mathematics. Others are trying to achieve geopolitical supremacy building artificial intelligence and robots armies.
Mathematics is blood. Mathematics is power.
There's a disconnect between academics and how real humans think if the modern solution to Math education is proofs.
I mean, there are definitely issues with the whole "forcing them to learn" part, but assuming we're given the option to change the content of the math curriculum but not to fundamentally change the education system, then yes, absolutely. You don't need a crazy level of rigor, of course, but I think learning simple proof techniques could make students experience mathematics more like solving puzzles than just completing calculations.
We can talk about why the teachers don't know these things, but I think the real issue is American culture still sees math and science as something for pitiful, nerd-virgin dorks. You can try to sell math as this sexy, dangerous thing you use to win wars, but ultimately you will have to reckon with the image that most Americans have of mathematicians and scientists, which is illustrated in shows like the Big Bang Theory: they're ridiculous laughing stocks who use science as a kind of cope for not being socially successful.
Plus, tell me: how do you learn proofs? They aren't statements in a textbook that you just learn and recite like poetry. You have to learn to see them, to understand how all those moving parts fit together. When done right, teaching proofs is an exercise in illumination. I find it is more enjoyable all around when performed as a creative, exploratory exercise: give the students the axioms, set them lose on a conjecture.
Of course, for that you need a) Teachers who can serve as guides in the mathematical worlds and b) Students who aren't culturally predisposed to dislike mathematics.
Then the problems compound when they just give kids calculators without the kids understanding why the calculator works, and by the time they get to high school hope is lost because they have no number sense and we're trying to explain variables and such...often divorced from real life. I've found my kids get a much more intuitive sense of slope when I explain it as the rate of change rather than "rise over run" that they're so often taught in middle school. Give them examples, like amusement park tickets (it cost $50 to get there, then $70 per person) and have them incorporate that into a slope-intercept form. It just makes things so much clearer that they often don't get because they don't have the number sense and because many teachers don't understand/appreciate math.