The entire point of diagnosis is because a person needs help.

The point of treatment isn't to "fix" or "make normal" someone. It's to give them the tools needed to participate.

For example, someone with autism might be more prone to having a meltdown. What therapy does is give them the tools to both identify that they are on the verge of such a meltdown and to de-escalate themselves.

The point of treatment is to help someone take care of themselves, hold a job, and generally not burden anyone. It's also to help a person feel better about themselves.