While obviously you could and there’s plenty of good answers in this thread to why two motors (or even three or four), the typical skateboard design for EV’s don’t really leave the door open for it without taking batteries out to leave room for a transaxle. Energy density in batteries is low compared to petrol or diesel, and you want to utilize the volume efficiently.

Another point is that electric drivetrains regulate 100-1000 times quicker than fossil power trains, so having two motors doesn’t really have much downsides.

From a manufacturing perspective: You can build an RWD or FWD vehicle, and without changing any components other than wiring and wheel hubs (maybe a subframe) you can add AWD, just need to plug it in. On an ICE vehicle you would have different gearboxes and stuff when going from 2WD to AWD/4WD.