Next thing you know, the chronic mastubators will be demanding a private area and time to "take care of business." After all, isn't that a disease too?
Technically no, it's often just a symptom of a mental illness. Think of it as a sensory response stimuli, used as a calming effect sensation. Those with mental illness, more especially those with schizophrenia, are hyper-stimulated, to the nth degree, and are literally firing on all cylinders. Just one reason why they're often witnessed having a conversation with the radio, or a television.
Another good example would that scene in Man of Steel, where in the classroom young Clark can see, and hear everything around him for miles on a level of twenty, on a scale of 1-10. He was over stimulated, same thing here. It's a coping skilled, but one of course that is heavily frowned upon in social settings. But those with mental illness typically get hyper-stimulated when out in a public setting. They tend to isolate, so when in public they're scared, or over stimulated so they "self-soothe". By blocking out all the interference.
Some individuals rock back and forth for comfort, or have any other manner of odd OCD learned behavioral rituals. To help provide an escape from over stimulation.
Masturbation for men, at least with those mental illness, is more popular because it's like touching the skin on the arm. For example. You immediately feel the touch, from the hand. Well the head of the penis is like a hundred times more sensitive, than the skin on the arm or leg. Providing a more instantaneous, and powerful simulator response (reward-motivator response). There is also a neurotransmitter response of dopamine and serotonin released into the brain, during masturbation, which helps contribute to a quicker calming effect.
I commonly see this and many other examples of self-soothing, at work. The reason, being I working at a involuntary court order psychiatric in-patient facility, on an all male unit. The patients there are petitioned against their will, and taken away from their comfort zone, and now are in a strange new environment/facility, unable to return home, or wherever they feel comfortable. So to cope, and or to block out interference/or signals. There is often a lot of what a normal person, like you or I, would conclude as inappropriate public masturbation. But to them, they're just trying to cope, block out signals, interference and or feel safe.
It's one of the more frequent things that we have to do milieu management education groups for.