That just means that the person now has two problems they can't solve instead of one.
You mean the addiction and the underlying cause? On the contrary: by solve the latter you also "solve" - or, rather, resolve - the former. Once you know what drives you to act in a certain way, you can include the real reason in your decision-making: do you want to get high every once in a while to escape the feeling of inner emptiness, or do you want to, say, find people who will love you and whom you'll be able to love back? This kind of question wouldn't even be possible without finding out what has driven you to addiction in the first place, and this is exactly what allows for a path forward.
Basically, it's a better-informed decision-making.