They could. But they dont. Why? Because its main advantage in a manual chair is strength without weight. Although looking at that chair it doesent look like hi strength pre preg carbon but wet laid for pretty shiny marketing purposes and cheapness, but never the less it Could be done.
They dont in a powerchair because how would it help? The 4 components that are the heaviest by miles are motor/gearboxes. These are seriously heavy, like solid metal. Full of steel gears, copper windings, iron cores, magnets, steel casing, etc. You would do well to carry one very far.
Then theres the pre historic lead brick batteries. Typically 2 at around 60lb each! So thats another 120lb...
The chassis of an F55 for eg weighs very little. Its thinwall steel tube, actually exhaust pipe tube. Build this in pre preg carbon, and even if it had zero weight, you save just 10 or 12 lb. The wheels, tyres weigh more each. And the fancy seating, with its actuators can weigh absolutely tons.
So while nice, you would also need to go with smaller capacity lithiums at about 1/4 the capacity to save a HUGE amount of weight, and then to retain range etc, higher voltage brushless motors for efficiency and so less heat waste so they can be smaller and maybe fan cooled like your drill internally, and use carbon fibre wheels with tubeless tyres to further save weight.
Only then would a carbon frame make sense. Until you add "rehab" seating... So this too needs to be just as light, or the chair will end up still heavy and also top heavy.
This is all beyond the average powerchair company engineer, and so wont happen.They all seem to work on "bits". A committee. There seems to be no one guy with a vision that can see how all this goes together. So the frame guy may suggest it, but the bean counter, and the guy in charge of total weight, see no benefit, only expense. So instead they will offer a new colour.