actually no - in many many cases of addiction there is a deficit of certain neurotransmitters in certain areas of the brain - such as dopamine is the mesocortical channel
recreational drugs often temporarily alleviate this deficit - satisfying a craving - but unfortunately become addictive and are not administered at therapeutic doses - as well as not having a reasonable therapeutic half life
of course thats not the case for everyone - and some people are just self indulgent twots
but mental illness and addiction can often go hand in hand - due to this neurotransmitter imbalance