Thanks. And yeah, this mostly works with a smarter, Morrison-esque Clark, less so one who is just an average idiot who happens to have powers. But to my mind, if you're writing Clark as a "normal guy with powers" then you're doing it wrong anyway.
But we already have that question in front of us with the Fortress.
Forget a durable fabric, Clark has the answer to almost every big problem humanity faces sitting around the arctic, collecting dust. Why hasn't he shared that tech and knowledge with us? The stuff he's collected, from Krypton to New Genesis to Rann and Thanagar, could solve the energy crisis, world hunger, cure tons of diseases.....
This is a question that basically every hero brings up if you think about it too much. They all have knowledge, skills, and/or resources that could change the world in huge, fundamental ways....but don't. Clark inventing a fabric that won't leave him naked after a fight is such a minor issue in this regard it's not even on the list.
Now that I think about it.....a durable fabric isn't even a good business model. Presumably your production costs would be high, and your customers will only have to buy from you once because they'll never wear out or ruin their clothes. You'd just end up with a warehouse full of jeans that're hard and expensive to make, that no one wants to buy because they already own one pair, and that's all they need.