I get your point about the real life side of football, the difference between the men and women's games are completely different. At the same time, this is a video game that yes mostly men play but there is also a female player base, EA does not want to seperate them off from the rest of the base so they mixed it.
A lot of people like using the female player's because they are more meta, it has nothing to do with them not being interested in football. Most people just take it for what it is, a video game that is not super realistic, and they will take anything that gives them an edge in the game.
As with real life football where most people say they don't enjoy watching the women's game, a lot of people wouldn't take any interest in playing the female game modes, which was also most likely tested when they first introduced women on to the game. Personally, it doesn't bother me one bit and in it's own way helps to promote the female game.
Yes it is unrealistic, but there are actually many reasons that it has been done, just take the most obvious reason that it adds more players to packs reducing the odds that we get something good, and increasing the odds that people use the store.
Personally, I have quite a severe dislike for the predatory tactics that EA uses, but as long as no government says it's illegal they will keep doing it. It doesn't mean they are wrong to include women in ultimate team mode, and I would hazard a guess that most people wouldn't be for or against removing them, they would just take it as it is.