It's fascinating! I love learning about linguistic changes through the centuries but when it's happening in real time I wanna know the reasons :D

It might be like the difference between "harmful" and "harming". Something that is "harmful" has the potential to cause harm, whereas "harming" is the act of causing harm. "Addicting" may be a nod to the lack of agency experienced by an addict. Addiction is being done to them, not by them.