Why is it illegal for prisoners to masturbate?

Question

I was was watching a prison documentary on youtube and one of the prisoners got caught masturbating in his cell and was wrote up for it and sent to Solitary Confinement.

Why is masturbating in prison illegal for the prisoner?

Answer 1

I think the reason it's illegal for prisoners to masturbate is because of the female prison guards.

The prison guards get offended by the males masturbating in their prison cells when they make their rounds and look into the prison cells and see a prisoner masturbating.