You can place the same argument on any chronic health condition. I have asthma and need inhalers every few months - I get charged for two prescriptions each time. If I didn't have the inhalers and had an attack, I could die.
I also have a chronic health condition which means every quarter I need to get an antifibrinolytic and a prescription anti-inflammatory. They don't work independentlly for what I have, but again, I have to pay double. I don't get quite enough prescriptions for it to be worthwhile to get the prepay, so I just dole it out each time.
You could go on to say why aren't tampons available on the NHS? Why should women have to have that additional cost burden?
I totally disagree that women's health should be classed as anything other than equal importance to men's!