The hairline itself is different between men and women like many other differences in our bodies. In other words the distribution of follicles is different. Extend this to gene receptors and the distribution of follicles with varying gene receptors is different. At puberty, the hormonal changes are quite different with different male and female sex hormones.
All in all the differences are like any other differences between the two sexes and its all in the genes for the most part. However there is generally better understanding of reasons behind male pattern baldness than FPB which is quite unfair to be honest. Women also cannot use the higher concentration of Min above 2% and generally cannot take finasteride. On top of this women cannot buzz their hair like men (in terms of social acceptance). And hair loss in men is more or less socially acceptable unlike for women.
Sorry for the depressing post but I know a few women (friends, partner, relatives) who are quite worried about their hair loss and I really feel that they deserve more, and not less, proven treatments and clear plan of things like Big3 exists for men. I don't understand why women hairloss industry is more focussed on concealment than treatments for some reason.