The BCG types are raging narcissists and thus incapable of love. It makes sense they wouldn't understand a set of characters completely defined by those concepts.

There is a reason Harley Quinn is so popular. The eternal victim of her awful boyfriend, who she always goes back to, who gets away with doing all sorts of awful crap because she is totes the victim guys. And she gets to be as crazy as possible while getting everyone's sympathy. The narcissistic female's dream.