Because aluminum has a lower current carrying capacity (EV's have relatively high amperage, compared to transmission lines - 30A-50A vs 1A). And the greater res

Because aluminum has a lower current carrying capacity (EV's have relatively high amperage, compared to transmission lines - 30A-50A vs 1A). And the greater resistance means a larger cross-section(~1.5x) than copper, which in a space-constrained environment is a problem. Also, access to aluminum means trading with China, Russia, or India - which means inherent geopolitical threats to your supply chain. (Copper is Peru and Chile, so somewhat less contentious) Are these issues solvable? Likely. They are, as the adage goes "just engineering problems". But they aren't solved yet, and that means, if you run a business, you hedge.