The intention is because if you are part of a minority group that disproportionately struggles or suffers or cannot access certain aspects of life compared to average or the majority, it is helpful to be able to identify members of this group.
It helps members of the group identify each other, so that they can swap tips and advice about what does work, and offer peer support and understanding. This helps people feel less alone. If you are part of a minority group, sometimes it can feel like you are the only one if you're only looking at the people you come across naturally e.g. through school/work/neighbours/friends of friends.
It helps scientists/researchers study that identified group to see whether there are commonalities or patterns, try to find out whether there is any likely underlying cause or mechanism, whether certain advice/approaches/therapies/medicines can help them.
It helps doctors, psychologists, psychiatrists, cousellors, therapists etc to help people - if they can look at a textbook or research or treatment guidelines and see what usually helps people in that group, or they can say actually, I haven't treated many people in this group but that other person is a specialist/expert in it - I'll refer you to them.
It gives a name to a thing so that awareness can be raised generally in public so that people can have more empathy - e.g. somebody today might be more likely to recognise certain behaviour as being associated with autism rather than misreading it as hostile or rude. Because autistic people are a minority and you might not know someone who is autistic personally.
If you take a completely different type of label or identifier, e.g. "gay", can you see how it's helpful? Gay people are in a minority and so it is helpful to be able to visit gay clubs, gay dating sites, or set their orientation on a dating site etc in order to find other people who they might want to date, whereas if you have to guess at everyone's sexuality through randomly meeting them it would be much harder because the majority of people are heterosexual. Years ago, most people were prejudiced against homosexuality and thought it was wrong, now with awareness raising and Pride etc, most people understand being gay is a perfectly normal and healthy variation of human sexuality, and that prejudice against someone because of being gay is hurtful and wrong, whether or not you are personally gay or close to someone who is gay. While the medical side is not relevant in this case, and has even been used to harm the gay community in the past, there has been research etc which is impactful and relevant to gay people, there are health issues which have disproportionately affected the gay community which need research and attention, and there are wider societal changes which have been made e.g. recognition of same-sex marriage, protection in law against discrimination.
The argument about whether or not neurodiversity is a medical issue which needs "fixing" is a valid one, but I think the grouping together of people with similar experiences and characteristics so that they can receive support, clarity and better understanding is usually helpful. The important thing to me is that medical interventions should target improvements in life or reduced suffering for the target group, rather than targeting "making this group more like everyone else".