Why search for a label?
Well, if someone's brain is well-balanced, the person can take in different viewpoints but still make up their own mind, they can regulate emotions without pushing them down or exploding, they can take in new information without overwhelm, they are flexible when needed, but hold good boundaries when needed. If the brain is not in balance, there's a good chance there are struggles. "Neurodivergent" is just a more positive term than "brain imbalance"
Now, that being said, who do you know who's perfect? Nobody, right? I mean, when is it a brain imbalance and when is it just a different way of being that's equally valid? So, indeed, why does the label "ND" have to be slapped on?
Because we want to understand what's going on so that we can adjust our expectations and behaviors. If someone is neurodivergent, you can start to anticipate their behavior, because you've got a framework to explain them by. It actually helps to remove some of the blame from the person. They didn't choose to be easily overwhelmed, or quick to get angry, or shut down, or....
It takes a lot to be a well adjusted person. Acknowledging that there are powers outside of just "try harder" that make up a human being helps deal with it all.
Abuse and ND?
You could see this as two one-way streets.
If there is abuse, there is often something wrong with the brain.
But if there's something wrong with the brain, there isn't necessarily abuse.
So what if you encounter abuse, is it logical to investigate if there's something wrong with the brain? I'd say yes. Even today, there are people with traumatic brain injury, for example, who get no follow-up, no psycho-education, no reach out to family. People are on their own and they don't always realize that it's brain injury that's at play, even if they do tell each other "(s)he changed after the accident". The person with the brain injury is often blind to their own behavioral changes and might suffer from dissociation or splitting. Same for hereditary issues and environmentally acquired brain disorders. Someone suggesting to an OP it's "ND" might actually be the first time that the OP hears of it. Yes, the internet repeats itself, because frankly, people's lives repeat themselves over and over..