My guess is that the disciples were no dummies. They could see where all this was going. If they were sent out like the Father sent out Jesus, it was going to be to walk in his footsteps. Jesus had given everything he had and everything he was away, not only for his friends and his family but for people who had no idea who he was, and even for his enemies. If they left that room it might mean that they would have to do like Jesus did.