Bingo. In fact you can guarantee that the majority of the people posting in horror here don't buy PES games and wouldn't even if they did include female teams and tournaments.
Spending a non-insignificant portion of your budget to appease people who aren't and never will be consumers doesn't make any sense from a business perspective if you're barely managing to compete against FIFA and have a fraction of the budget.
I get that a lot of us feel strongly about this issue, but implying that the ability to play as women in FIFA is somehow a driver of sales isn't backed up by the evidence:
PES simply doesn't have the budgetary luxury like FIFA of including the women's game no matter how much they would want to.
This is exactly the reason and it's obvious.