There’s multiple motivations that can lead to this. One that comes to mind is
depersonalization which can be triggered by stress, trauma, or neurological conditions. For some the feeling of being real is achieved through feeling pain and some prefer to feel pain than to feel like an inanimate object. There’s more to it than that, but that might be enough to get you started on understanding.
This get’s into motivation theory. Often times there are multiple factors behind the motivation for someone’s behaviour. There may be awareness that a habit can eventually lead to life altering injury or death. But that might not be the objective of the person that is engaging in the behaviour. In the case of certain drugs one of the results may be temporary relief from from other condition within someone’s life. A recent study of addiction looked at why people that have been a pain killer that is similar to heroine in a hospital don’t generally become addicted and go looking for it after release from the hospital but others are addicted. It seems that what’s going on in one’s life emotionally is a significant factor.
There are behaviour prescriptions on which I’m sure many people within the same culture can agree, but I’m not sure that there’s going to be compatibility in what someone feels is right or wrong
in the back of their mind. A recent example that came up in discussion here was a man that owned a pizza shop here in the Atlanta area that did an honor killing of his daughter. When the police arrive they were some what confused at him plainly stating that he killed her daughter without any and sign of fear, hesitation, regret, so on. I can’t say with confidence that he felt the honor killing was wrong in the back of his mind.
[SIGN]But that would establish mens rea pretty well.