There haven't been many studies on treatments for people with schizoid personality disorder, mostly because they don't tend to think anything is wrong. They just don't like being around other people. They also don't cause many problems for society like people with antisocial personality do. So while they may seem weird to people around them, they aren't too likely to come in for treatment at all.

Borderline personality disorder is entirely different. People with borderline personality disorder absolutely know that something is wrong. They feel great distress and so they go in for treatment. Some of the symptoms are very dangerous too, so it's very beneficial for society in general for us to find effective treatments. And there are some. It's not hopeless. It's complicated and difficult, but people can recover from it or at least manage it.

Also, not all people with personality disorders are the same. Some will have better success than others. There's a whole host of other variables such as income and ability to pay for treatment, intelligence, motivation, and support systems that all influence treatment success or failure. It's not unlike diabetes. A person with a relatively high income and health insurance will be able to afford the cutting edge drugs and healthy food needed to manage it. If she has family and friends that support her and motivate her to take care of herself she'll have better success too. If she lacks those things, she's likely not to do as well.

And probably like diabetes, a personality disorder is something that a person will have to be aware of and manage for the rest of her life, but just because something isn't completely curable, it doesn't mean that there isn't hope to have a much improved existence.