Because change means no longer being a victim - and most of us have had our addictions taking control for years, often decades. (We’ve been living in “my addiction wants this and it does what it wants - my substance / addiction is king and tells me what to do”.) it’s scary because you are literally standing up to a bully: your addiction, which has been bullying you for years.
Sassy has a good list of her reasons for staying sober - it helps her. Take care & don’t give up!