Well borrowing money isn't that bad but the worst thing is that such addicts sell their household things and belongings of their siblings and other family members.
It's not bad if it's put into good use. But if it's used for gambling, that's how the worse part starts. And this isn't just a tale and it is really happening. Gamblers selling their stuff to fund their gambling addiction seems to be a common thing with most of the addicted ones. They could even sell their souls and bodies just for them to get funded, we see people do crazy things for themselves just to do their thing.
Sometimes gambling addict will have an impact on the people around him and can also cause losses by borrowing money and there is no certainty in returning it or even as @SamReomo said with an addict who sell their valuables household.
This is condition that sometimes creates bad thoughts in society about gambling addict, and of course an addict continuously if not treated and there is an effort to cure it then it will be like chronic disease and can have very fatal consequences in the future.