Why are there separate tournaments for men and women? Why are there separate tournaments for men and women?

It is obvious that in physical sports men have a huge advantage, but what is the reason why in chess we differentiate by gender?
Chess as an activity is not appealing to many women. Because there are so few women in open tournaments, it can be quite intimidating for a girl or woman to start playing the game. Imagine being one of the 1-3% of female players at a large open tournament. They receive constant attention and stares (it is much worse if they are conventionally attractive). Some women like this or are not horribly pushed away by it. Many are.

Thus, girls-only tournaments were born. In the US, there is a National Girls Championship every year near Chicago which attracts 200+ participants. This is a place for them to play without having the pressure of being basically a foreign entity at most open tournaments. I think that scholastic tournaments for girls are a very positive part of the chess world.

On the other end of the spectrum, and what I don't like, is the structure of the Women's World Championship, Women's Olympiad and various national women's championships.

My basic issue with these events is that they essentially encourage top women to get to a certain point (about 2500 Elo) and then stop improving. Take the history of Olga Girya (http://ratings.fide.com/hist.phtml?event=4195752) for example. I count 23 events that she has played since Novemeber 2012-the last time that she played in an open tournament. In many of those 23 she played not a single woman that was higher rated than herself. She has been making plenty of money, but her growth as a player has been stunted by playing in such a closed pool.

Irina Krush, in the US, recently made GM. She has been playing in US Women's Championships since she was 14 and has been one of the top two or three seeds for maybe the last 10 years. How much better would she have been if she had instead been competing against the best players in the country in the Open championship? I think it is almost unquestionable that playing against inferior opponents so often been a detriment to her improvement.