The constitution says so and at the moment it's unlikely for a qualified majority to be found to change it. It's as simple as that.

> Why is it only *forced for men?

Because since mass armies are the case it always was so, and all can men do now is whine on the internet, because they are not going to do anything.

> Does that sound equal and civil to you?

Not really, but however it sounds has no impact of it being the case.

> note we are not living in middle ages

In middle ages most men had no obligation to fight wars.