Of course it's important. Vital in fact.
Women are disadvantaged by their biological sex. They are not looked over for jobs because they like to wear dresses, or have long hair, they are looked over for opportunities in the workplace and elsewhere because they are "a risk" for maternity leave. Whether they're infertile, gay or choosing to be childless, they will be treated differently to men on the basis of their potential biological functions.
If we no longer classify humans by definable biological sex, the ability to track this stuff becomes lost. How do we monitor who opportunities go to? Who earns more? Who retires earlier in better pensions? Who works full time the whole time and who loses out by taking on society's caring needs? How can we possible jneonwhat were talking about if it's all based on self id and changing, shifting definitions. How can we draw out any conclusions and mitigate any disparity?
In healthcare, women and men have different reference ranges for really important blood tests. Kidney function, cardiac function, haematological functions...you'd all be giving the wrong treatment for the wrong things if you behaved as though sex didn't matter. Blood transfusions are known to be far riskier in some circumstances if different sex blood is used.
In sport, biological males have massive physical advantages over women. If we had no sex based categorisation, women would win nothing, ever. Why is that a good thing? They'd sustain more injuries and receive no prize money either.
In crime reporting and the justice system, how do we know what leads to certain sorts of crime, who is at risk of being involved, what works to change that trajectory, what kinds of crime are committed by people with certain experiences and how we can mitigate and reduce offending?How can we monitor what impact various CJ interventions have on both the offender and others? Like the report on the news this morning about parental imprisonment and the increased detrimental impact on children when it is the mother incarcerated.
How can we plan public services to meet the needs of populations if we deliberately make it harder to know who it is we are trying to meet the needs of. How do we ensure we meet public sector equality duty without due respect and accuracy when collect data about protected characteristics, of which sex is one?
We can be kind, accomodating, respectful and acknowledge someone's firmly held beliefs about their completely abstract ideas around gender identity. But we should never do this at the expense of maintaining a grip on reality and dealing in hard, immutable facts, like what biological sex we all are.
Quite apart from all that. I don't have a gender identity. I feel a bit weird every time I'm expected to tick a box and buy into the idea that I do. Just the same as I'm an atheist and therefore don't want to pick a religion from a list, I choose the "do not have a religion" box.
I know a lot of people, personally, professionally, socially, through school, and not one of them has ever referenced their gender identity in my interactions with them. They all know what sex they are though.