I don't think it's an addiction in the traditional sense of a substance addiction but an addiction to the lifestyle - to being one of the biggest and the best and having people look at you and say 'i want to be like that one day' - which, let's face it, nearly all of us have thought at one time or an other. Whether it be looking up to Arnold in Conan or Lou in the Hulk as a kid or something more recent (for all you budding Ronnies out there).
One of the most important points,as @
Rugby88 ; pointed out is that for many of them it may represent an opportunity to make substantial money for them and their family
if they can secure sponsors and become a top tier pro. An opportunity that may otherwise not be available to them. The problem being that their are no shortage of budding pros willing to take these risks to reach the peak of our sport and unfortunately limited places to fill.
I think all of these guys are well aware of the potential risks and you'd like to think that the risks they take are calculated risk/benefit decisions. Unfortunately this is probably not always the case.
Regardless, it is a sport I love (despite all the dysfunction within), and everyone will make their own way through their lifting 'career' and make their own decisions. So whether you are natty, get on a couple of times a year or are a gear fuelled beast and life is one big cycle, you should never forget that without your health you wont be lifting anything - and good health can be fleeting.