It traces back to cultural and educational issues.
Math has typically been taught devoid of any context or relevance to our everyday lives. Even in college, you just mindlessly plug and chug formulas to get by. Some students don't see the use in it, beyond perhaps the parts needed for basic financial literacy (which many do not have, either).
Better and more engaging and relevant and effective ways to teach math have already been developed, such as Realistic Mathematics Education.
But people actually say things like "I can't do math" in regards to all forms of literacy, I believe. It depends what standards you are mentally comparing yourself to, I guess, such as professional vs. social standards.
"I'm not good with money, or I'm not good with the business stuff" - financial literacy
"I can't write" - as in, I can't write books or novels or easily do other professional writing tasks. Again, there are pedagogical techniques that can help students write more, write better, and have more interest and confidence in writing.
"I don't read" - most folks nowadays don't really read books or novels anymore, what with TV, movies, and the Internet.
"I don't know computers" - how often do we hear that - that's computer literacy. I hear it less and less though nowadays.
To tell you the truth, maybe it will be nice when one day people feel forced to admit "I can't code." Because that would mean that programming and computational literacy is something taught in most schools.
My wife is a public librarian, and occasionally comes home with stories of people she had to help with the computer. Patrons are allotted one hour of computer time per day, and she says it often takes that much time just to create a gmail account, compose an email to <government office> and send it. The mouse seems to give a lot of people trouble, which blows my mind--I first encountered a mouse when I was a college sophomore and one of the first Macs appeared on campus. "What's this thing?" I wondered, reaching for it. When I touched it, I noticed the arrow on the screen moving. It didn't take but a second or two to realize that moving the mouse caused the pointer to move in similar fashion. It seemed obvious to click the buttons on the mouse to see what happened, and discover, in about a minute and a half, that a single click selected whatever the pointer was touching, and a double click activated it. How can people not grasp that connection intuitively?
But the sad fact is, there are a lot of people who don't grasp that simple cause and effect relationship, and you know what? Those are the people in your neighborhood... they're the people that you meet, when you're walking down the street. They're the people that you meet each day!
I completely agree that it traces back to educational issues. In fact, i recently wrote an article about this problem - http://aditgupta.me/post/what-is-17x13
My post was, in context, not about the Internet, it was in response to your comment in reference to:
"most folks nowadays don't really read books or novels anymore, what with TV, movies, and the Internet."
Comparing reading a 3-4 paragraph article on HN (or elsewhere) as being the same as reading a book or novel, the "rest of my post" was an anology.
True, those people that don't read ebooks or longer articles propably were not reading books or novels to begin with, so it is a win for literacy, but its just as likely they just shifted to that because it's easier to read an article off their phone while shitting than turning the pages of a physical magazine.
So TLDR; Reading articles online isn't the same level of effort as reading a book, which your comment seemed to support.
Math has typically been taught devoid of any context or relevance to our everyday lives. Even in college, you just mindlessly plug and chug formulas to get by. Some students don't see the use in it, beyond perhaps the parts needed for basic financial literacy (which many do not have, either).
Better and more engaging and relevant and effective ways to teach math have already been developed, such as Realistic Mathematics Education.
But people actually say things like "I can't do math" in regards to all forms of literacy, I believe. It depends what standards you are mentally comparing yourself to, I guess, such as professional vs. social standards.
"I'm not good with money, or I'm not good with the business stuff" - financial literacy
"I can't write" - as in, I can't write books or novels or easily do other professional writing tasks. Again, there are pedagogical techniques that can help students write more, write better, and have more interest and confidence in writing.
"I don't read" - most folks nowadays don't really read books or novels anymore, what with TV, movies, and the Internet.
"I don't know computers" - how often do we hear that - that's computer literacy. I hear it less and less though nowadays.
To tell you the truth, maybe it will be nice when one day people feel forced to admit "I can't code." Because that would mean that programming and computational literacy is something taught in most schools.