There are obvious practical reasons to learn to cast with your off hand. A few years back, because of injuries and degeneration, I had to have my right wrist fully fused. A titanium bar was inserted from the back of my middle finger/upper knuckle, up my forearm and screwed in along with the wrist bone being replaced with hip bone and then fused. May I just say that it is a very painful surgery/recovery if you consider it. That said, years later, my right hand is slowly suffering loss of sensations and swelling/pain in the knuckles.
A full day of casting (maybe catching) eventually makes the right hand give out. I have learned to ease this gradual decline by casting with my left hand/arm. I have never progressed beyond a single haul, but I can get the line out via roll casts and normal casts. The right hand is able to do the normal line retrieval. Because my reel is still set up for left hand cranking, if I do hook a fish I still have to revert to bringing the fish in with the normal right hand holding the rod while the left hand cranks the reel or strips. But, that occasional casting with the left hand helps. It also helps when the lay of the land necessitates a different casting presentation.
Also, there are theories that doing endeavors with your off hand, arm, foot etc. actually may improve your performance afterwards with your dominant side. I recall my son’s venture into throwing the javelin. He had smaller practice javelins/darts and he was encouraged to also practice throwing with his off hand and practice his footwork to support that off hand approach-throw. It seemed to work…for whatever reasons. The same seems to work by casting with your off hand.
Not only do you expand your tactical possibilities, but you may well improve your strong side casting abilities. Worth a try.