I'm curious why exactly they haven't made 2-3 speed trans typical in EVs already, like Porsche did. Single gear is too inefficient at freeway speeds. Tesla supposedly solved this with dual-motor models where the second motor has a different final drive ratio, but I feel like that's more expensive than 2WD w/ trans, which doesn't need to be nearly as advanced as the ICE-driven kind.

To my understanding the increase in efficiency is marginal at best, highway efficiency is completely dominated by wind resistance in either case. It would never come anywhere near paying for the increased cost or complexity of implementing the transmission. It may not be quite as complex as a five or six speed ICE transmission, but my bet is that it is much closer to that end of the scale than it is to a single speed reduction gearbox.