Dear friend,
My opinion only. Watching PORN to many is more like nothing wrong done at all as they are not hurting anyone directly. Do you know why it's a sin in God's view?
Hypothetically, think of family members who are close to you. (Mom, Sister, Daughter, Son, etc.)
Will anyone be able to watch PORN if any of their close family members are involved? I would say 99% will definitely say NO to it as they love them and can't see them in that condition.
God treats every human being as His son, daughter, and that's the reason it's a sin to watch PORN.