I mean… if there was really widespread demand for it, you could make something AA-cell sized that is actually two smaller 1.5V cells stacked in series. That’s basically what a 9V battery is, it’s six little 1.5V cells packaged up.

But most things that want 3V or more have enough space to hold two or more AA or AAA cells. So there just hasn’t really been enough demand to make a new widespread size+voltage format for consumer usage.