What are all the possible reasons why women are leaving tech/engineering jobs more than twice as fast as their male peers?

Male dominated environment can be very difficult to handle as a young female engineer. If there have been some pioneers before her and some role models in the company, then mentalities should have evolved and she should be fine. But being a pioneer requires some special strength. You have to fight the unconscious bias, and the daily sexism. The later can be quite tough. These are small remarks or jokes.. except that you are alone, and it can be repetitive to the point of breaking, when most people will wonder why you don’t understand it is just a joke!. Also, you might not find support around you, of people who really understand what you are going through
The second reason will be the career. People tend to promote people who look like them. If there are not many women, they might not get the same promotion. If we add to that the fact that many talented women remain quiet and are not so easy to identify, it will take special manager to go and look for them. They might leave before that.
But the main reason is quite often the kids. Again, by lack of role models, many women don’t think that it is possible to have both, career and kids. I am a living example that it is feasible but the society makes mothers feel guilty when they go to work. The pressure is such that many will stop at that stage. If they do because this is what they really want, great. But unfortunately it is often for the wrong reasons. On the same topic, many women will sacrifice their career to the one of their husband when there is mobility involved. Not because his job is more important but because culturally, this is what you do! In some companies, not being mobile can be a real handicap.
But things are changing! More and more role models, more and more women networks to help, more and more companies fighting sexism.. etc. Hopefully, one day, gender diversity will be a topic of the past even in STEM