This is a rather complex and somewhat taboo - ish topic. Firstly, masturbation is a normal part of human sexual expression but it is meant to be a private activity. Story - telling, on the other hand, can be a public or private form of communication. Combining them in a way that implies doing both simultaneously in a non - private context is inappropriate. In a private, consensual, and adult - only setting where all parties are comfortable with the situation, it might be a different story, but in general public and social settings, this would be considered unacceptable behavior as it goes against social mores and privacy expectations.
Masturbation is a private and personal act. Combining it with story - telling in a public or inappropriate context is not considered proper behavior. It should be kept in the realm of private and appropriate personal time.
Well, in general, masturbation is a very private matter. Story - telling is usually a more public or social form of communication. Mixing the two in any sort of overt way is not socially acceptable. We should keep private activities private and respect social norms.