The Half a Therapy trap
Often, what lies behind "I've tried therapy" or "I'm in therapy" is really : half a therapy. Let me explain.
They love the begining, the novelty, and THE ATTENTION FROM A BRAND NEW PERSON they can sell their sob story to. And it is necessary for the therapist to be all listening at the begining, and let the patient tell what they think is happening to them. The therapist will also guide them with psychology lingo that they can weaponize later. They love that first phase, as it provides attention, "explanations" for behaviour that are likely to become excuses, even if they claim it's just an "explanation".
Maybe they'll even learn some coping mecanism, how to manage big emotions, it feels good to be in control. Most PwBPD crave for more control over their own emotions. So you think "wow, this is getting better ! So much progress in 6 months, can't wait to see what'll happen in a year or two !".
MISTAKE
Then the rest of the therapy has to start, and it's the accountability and change part, and they hate that part. So then, their therapist suddenly becomes a problem, "toxic", ableist, classist, homophobic yaddi yadda... Their therapist is not "understandiiiiiiiiiiiiing". They are misunderstooooooooood. And the cycle goes on and on again.
Now a half-therapy PwBPD can do a lot of damage, because they are able to hide the red flags, mitigate big crisis, look more normal in public setting. But they'll still use you as a human toilet paper at home, while never loosing their shit in public.