I think that too many people still hold views similar to my father about females. We are, according to them, naturally slow witted, emotionally over reactive, and either terribly shy or jabber mouths. We are supposed to learn slower, cry, scream, throw tantrums more and, either hardly talk at all or, talk incessantly.
That presumption is enough to mask any thought that we might be on the spectrum when we are younger, so unless we are fairly low functioning, we go unnoticed. By the time we are teen, it's all blamed on hormones and teen drama, or we are diagnosed with Bipolar, BPD or Depression and given meds for that.
By the time we are adults, we have some Dx in our records and, it's difficult to convince anyone to look beyond that, to think that might be in error and, something else is going on with us. By now, eve we ourselves may assume the Dx is correct and never seek anything further, just assume we're female with that problem so, that's how it is.
In general, people find it easier to dismiss the outwardly displayed aspects of ASD in females as something else, or just being female than they can dismiss the same things in males.