Question

Why can’t conductors generate static electricity when rubbed together?

Answer 1

static is due to an imbalance of charge on the surface of a material - as it makes contact with another, electrons "jump ship". an electrical conductor, if it loses or gains an electron, can even/ smooth that out by allowing the charge imbalance to distribute through it's volume. with a non-conductor, you are left with a localised charge imbalance.

in addition, or similarly, a conductor is less likely to have an affinity for extra or less charge, as it is already well balanced because of its conductivity.

but google "triboelectric series" and see that things like aluminium feature on there, albeit in the middle of the series, for good reason.