If you want to artificially limit torque, sure. But it generally isn't necessary.
The only attempts at production EVs with multiple gears have targeted two gears, one for acceleration and one for increase top speed above 100mph for racing or Autobahn cruising.
That's not going to give drivers the "thrill" of a manual transmission.
If what you are seeking is the direct-drive feel of a manual transmission, and shifting to be in the strong part of the power curve for each situation, an EV does all of that just by pressing the accelerator.
The Taycan shifts into second at 62mph. Seems it's not just for racing, it's also an efficient freeway cruising gear loosely comparable to overdrive on ICEs.
And I imagine even the single-gear EVs have a final drive. What if that ratio were adjusted to be shorter?
If the Taycan didn't have two gears, they would have optimized for efficiency at 70mph, with a compromise of decent (not crazy) acceleration below that speed and a falloff of acceleration power over 100mph.
Since it has two gears, they were able to make one shorter for acceleration and another taller for top speed.
Tesla does something similar but by using different motor types and final drive ratios on each axle.
If you gear an EV for highway speeds with a single final drive ratio, (this is what most EVs do) then you get acceleration better than most midrange gas cars, good highway efficiency, but acceleration power tends to fall off at speeds over 80mph-100mph.
The reason to add gears is if you want even better acceleration and/or better high speed performance.
The base-level Teslas only have a single motor. If it's geared for highway speeds, I imagine it's less efficient in the city than it could be with another gear.
Does max power output correlate with efficiency in EV motors? I know it doesn't in ICEs.
The efficiency and power curves are much broader for EVs than ICEs. The RWD Tesla Model 3 is one of the more efficient EVs on the market altogether even with a single motor and single speed. But it suffers in acceleration compared to dual motor models which use a less efficient (but higher low-speed torque) induction motor with a shorter gear ratio on the front axle to boost traction and acceleration.
Think of it this way, if the Taycan were to drop one of its gears they would drop the low gear, not the high gear. The car would still accelerate better than most midrange ICE cars and still do fine on the highway. It just wouldn't have the off-the-line punch you expect from a high end performance EV.
If you chop the low gears out of an ICE transmission you either just stall or have extremely poor acceleration at low speeds.
So yes gearing can help in an EV if you want high performance over a large range of speeds, but for a city or highway commuter car, even chasing sportier characteristics, single speed (per axle) is fine. If you want two ratios for overlapping performance you can just change the fixed reduction ratio on one of the axles.
The Taycan is specifically targeting a range of performance beyond what you'll use daily on US public roads.
It'd also lose energy to the gearbox, would weigh more (more energy loss), and would cost more. It's not obvious that the efficiency would be improved.
Basically EVs have such a flat power curve to such high RPMs that a single speed really does cover most use cases. Two speeds can help if you are chasing performance.
Any more gears than that and I think you are just adding an artificial game for the driver to play.
The only attempts at production EVs with multiple gears have targeted two gears, one for acceleration and one for increase top speed above 100mph for racing or Autobahn cruising.
That's not going to give drivers the "thrill" of a manual transmission.
If what you are seeking is the direct-drive feel of a manual transmission, and shifting to be in the strong part of the power curve for each situation, an EV does all of that just by pressing the accelerator.