Because addiction is an empirical behavioral phenomenon (you can't stop taking it and it makes your life worse) whereas tolerance+withdrawal are physical phenom

Because addiction is an empirical behavioral phenomenon (you can't stop taking it and it makes your life worse) whereas tolerance+withdrawal are physical phenomena that correlate with, but are not, addiction. Current understanding is basically "addiction means not having your shit together," described in terms of predisposing factors such as stress, depression, physical dependence etc.