Question

Why aren't friction and tension classified as fundamental forces?

Answer 1

I would say because they are a kind of macroscopic aspects of electromagnetic forces.

Explanation:

From what I can imagine, friction, at a microscopic level, results from the electrostatic interaction between atoms of different surfaces in contact while tension comes, for example, from a change in relative disposition of the molecules inside, say, a rope causing an elongation of the entire structure (that can be erased when we stop acting on them) still from electrostatic interactions between molecules.