To comment at length on issues addressed well by @ff524's answer:
First, as a fact, in all my observations, at all levels of education, from k12 through advanced PhD-program stuff, at most 1/100 people create their own course material. That is, yes, 99/100 use something published by traditional publishers, etc. For that matter, probably an exact zero percent of high school teachers use anything other than what is mandated by their school board, which was not created by them... and they would not have been paid or compensated for creating anything anyway, so, ...
At undergrad level, a similar dynamic is in play: most universities, colleges, and even community colleges do prefer "tried and true" texts to anything that their own people might create. (See "prophet in their own land"...) So, actually, it's all the more certification of conformity that they don't use their own in-house material...
Returning to the literal question(s). Low level math is so intensely cliched that no one can claim much originality to anything at all... Ok, given that, can you complain that anyone's not original? No. They aren't original, and they know that, and everyone else does... and how many ways can we ask basic calculus questions? Or can we copyright "2+2=4"? Hopefully not. Nor need we compose original narratives about arithmetic algorithms using Hindu-Arabic numerals.
Nevertheless, a too-literal copy-and-paste of stuff off the internet is cheesy, cheap, etc.
Double-nevertheless, there isn't much room for "original" questions about 350-year-old, or 1,500-year-old, ... math. The fact that your "teachers" didn't create their own content is completely unsurprising, given the realities.
(I note that, due to my luxury of having a low teaching load, blah-blah, I can create more true-to-reality notes on many mathematical topics... But many people do not have a light-enough load to do this, and so on...)