When would they have the time and money to set aside to get deep into a subject that most of them do not have the academic background to see the value of?
Yes, everyone could learn mathematics. Just like everyone could get rich and go into space. It's just that for a huge proportion of people the pre-requisites are not there.
Ah the false analogy[1], we meet again. You don't really believe this do you? I mean you could make the same argument about gardening. Literally anyone can learn at least basic math, most people just don't have the inclination.
I feel particularly deceived about this state of affairs because my parents paid a lot of money for my formal education (school, university), and I got significantly less value from it than from people simply willing to share their knowledge for free.
Imagine me or someone else that was never part of the math research establishment came up with the exact same proof Perelman came up with. Ipsis verbis.
You can rest assured that at least the slack that they cut him on sketchy details would not be extended to an outsider. (In a way the Yau debacle was a manifestation of this)
There are a few examples of this already in somewhat obscure fields.
That's assuming anyone would even give the proof the time of day.
It might be worth thinking in this "math for and from the elites" mindset when describing public aversion to the subject. Seeing it as beyond oneself or not relevant to one's life lends little towards anyone's desire to learn anything about it.
It's easy to say "why don't they just do it," with some diffuse definition of "they" in mind, but even the most basic things can be hard to get for the poor. A proper maths education is one of them, I think.
https://history.princeton.edu/people/michael-j-barany
I'm troubled that a Princeton history student can write about a worldwide phenomenon with so little reference to non-Western cultures. (This is a pet issue of mine, as I am an American who lived in east Asia for years after studying Chinese and sinology.) I don't think he has looked at development economics and the history of popular attitudes toward economics enough to understand how important basic understanding of mathematics is. In other words, I disagree with the conclusion of his article, summed up in the last paragraph.
"Imagining math to be everywhere makes it all too easy to ignore the very real politics of who gets to be part of the mathematical elite that really count—for technology, security, and economics, for the last war and the next one. Instead, if we see that this kind of mathematics has historically been built by and for the very few, we are called to ask who gets to be part of that few and what are the responsibilities that come with their expertise. We have to recognize that elite mathematics today, while much more inclusive than it was one or five or fifty centuries ago, remains a discipline that vests special authority in those who, by virtue of gender, race, and class, are often already among our society’s most powerful. If math were really everywhere, it would already belong to everyone equally. But when it comes to accessing and supporting math, there is much work to be done. Math isn’t everywhere."