I won’t defend CCA wire but aluminium is an excellent conductor… by weight, not by volume. It’s not that you can’t make good aluminium wire it’s that CCA wire are generally shoddy. Brittleness is an issue but with time copper work-hardens so you can’t mess with it infinitely, either. It’s especially useful for overhead lines as it’s so light.

Somewhat not entirely unrelatedly: Steel bike frames are generally better than aluminium. They’re it practical terms about as erm sturdy at equal weight, but steel bends quite a bit before it breaks so a good steel frame will be lighter than an aluminium frame and can get by without shock absorbers when the geometry is good, that’s why you see curved forks (not if it’s a downhill bike, of course, and “generally” means “if you’re not looking for a carbon-fibre race bike”, there’s reasons to want stiffness in bikes just not for most people).

Next up: Oxygen-free copper and audiophiles. Practically no increase in performance (and definitely none compared to simply using more copper), meanwhile, so cheap that when you’re at a decent store (say, Thomann) and sort by price the cheapest stuff will have OFC.