I read somewhere that when a person develops an addiction that their emotional maturity is stunted at that age. I started using at age 19 and still exhibit many of the traits of an immature 19 year old. (I am now 49) I think that is because, as others have mentioned, you kinda stop living and experiencing the same things as a "normal" person while you give yourself over to the addiction.
Unfortunately, even without the addiction, it is really hard to just start "living" again after 30 years. Good work for me and my therapist!