Not all cuck hubby's are the same. Many are prone to an unwanted ejaculation when watching the wife being penetrated, orgasm and especially seeing the lover inseminate her. It is not appropriate the hubby cum when the wife and her lover are enjoying their connection, and he still has work to do to clean up all that semen when they finish. His work will lack the enthusiasm that the wife desires if he has already ejaculated. She will take care of his release later, maybe.