Because they have completely different mission parameters. Commercial crew is for ISS trips, so short duration trips, so limited life support or things like to

Because they have completely different mission parameters. Commercial crew is for ISS trips, so short duration trips, so limited life support or things like toilets required. Artemis needs to send a lander to the moon and come back. So 3-7 days with extended life support, and the ability to land on the moon with a vehicle and take off within the size confines of a single launch. Orion is for deep space exploration, no lander necessary, and extended life support. So yes, three completely different vehicles. The last time we tried to combine multiple roles into a unified chassis, the F35 happened.