Let’s try this. Put aside all teachings, religious, spiritual and such and only use your basic logic for a minute.
There is a system that is our body, which is working by order to fulfill all functions to maintain life the best possible way for itself. Since you have your own free will as a person, you can help this system working correctly, or you can do things that harms the system and ruins it’s functionality. This is true for instant harms, like suicide that can simply stop your system instantly, and also true for things that only slowly effecting your system proper ongoing, like bad eating habits, smoking, faping. Eating habit might not ever gonna kill you, and it is not definite that you will get cancer because of smoking, but you won’t be able run freely as a fat fuck, or with weak lungs. Just like with fapping. Your penis will not fall off due to fapping and you will still be able to pee, but you won’t be able to maintain a proper erection, because you will have ED. You see, it is natural to have consequences for bad habits if you do long enough. It is unavoidable. Don’t look for excuses to fap. Sometimes we don’t feel bad after fapping because we were able to shut out or numb our conscience.
Hope I was able explain properly and you get my point.
My personal opinion is that we are like this because originally we were created in a good order to live, but since humanity ruined it by free will, we have to face the consequences of our actions.