Is it permitted attend mixed gender social events/gatherings (e.g holiday events at a bar/club, concerts (without seating), where men and women congregate and socialize together?
Social intermingling between the genders causes a person to have inappropriate thoughts and it is a catalyst which brings people to frivolity, low behavior, and eventually to a forbidden relationship. Therefore it is condemned according to Jewish law, and should not be done. To be honest, this is exactly the reason why it is done by the gentiles, as a form of entertainment, and to get people’s hormones going. The gentiles don’t see anything wrong with it, and they find it entertaining, however to a Jew, the torah’s view of marriage and the relationship between men and women is for a lofty purpose. It is in order to build a family and to build the world, and not merely as an opportunity to experience pleasure. When the relationship between the genders becomes warped and denigrated into a lustful, self-pleasuring experience, it has many unwanted outcomes. Women become objects of pleasure and they end of feeling looked down upon and taken advantage of. People are not interested in getting married, and the institution of marriage comes into question, and when they do get married, they will be a lot closer to getting divorced, because to them, the main reason for the relationship was for pleasure. Besides this when a man or woman has already had experiences with numerous other people, it takes away from the specialness of their spouse, and that has a detrimental effect on their eventual marriage.
Therefore the torah’s view of relationships is that there should be a separation between the genders, until the time of marriage, then the two parties see each other as the only one in their lives, this is the only man in my life and this is the only woman in my life. This helps that their marriage should be a wholesome, faithful, fulfilling experience, that has a very lofty purposeful goal to it. Building a home, having shalom bayit and raising a family are seen as part of our purpose and job in this world, and it produces, families that function with a higher goal and motive, and it gives a lot of meaning to life. Therefore the torah does not want us to just socialize with people of the other gender.
Even Haezer 21.