A lot of it is because of the laws. Marriage is a very serious contract,...and it's heavily slanted in favor of the women.
If a man has kids with a woman,..she essentially owns him and the courts will back her up.
This^^^
Another reason for the MGTOW movement is because a huge number of young women in America today have had their brains turned to schitt by the feminist crap.
Western culture has been selling a fairy tale to women for the last 2 or 3 generations, and it is no wonder so many women are "disappointed" by so many men.