Yes, we have a moral obligation to develop our talents. If for no other reason but to aid those who come after us. The talents and abilities that we perfect or bring near to perfection adds something benificial to the world.
Actors provide a minor service, but a service none the less.
Developing their talents increases the ability to entertain. This is a service to the morale of all people at large. To provide such a thing to others is important to well being, and we all have that moral obligation to our fellow man. The only reason for this is that we essentially need each other. Man has a responcibility to himself and other men.