That's because "real knots" depend heavily on the material they are tied in. Many knots that work well in a hemp rope won't hold in slippery dyneema, even fewe

That's because "real knots" depend heavily on the material they are tied in. Many knots that work well in a hemp rope won't hold in slippery dyneema, even fewer will hold in fishing line. Mathematics wouldn't be the right field to investigate with such physical properties, so they simplify and remove the need for those properties altogether. Mathematical rope is infinitely stretchy and slippery.