"Who can say why women don't enter or stay in IT?" The person who has gone out and measured it, of course. Has anyone interviewed several thousand women who have the necessary aptitudes why they did or did not choose to work in computing? What did the stat.s look like?
May I also say that computing is not one field. "Computing science" is a branch of mathematics, and properly so. "IT" is running wires and installing and fixing stuff -- it's construction and maintenance, like plumbing. Programming is like commercial art except the artists have their brains installed backward. :-) User Interface design (including website design) is graphic art, and the artists are normal (for artists :-) . Maybe some of these should be spread over other disciplines, and some should not.
I left out "software engineering" because I'd like to hear opinions from current Professional Engineer holders as to whether software engineering is engineering. Whatever it is, it's a management discipline, about as far from science, design, or plumbing as you can get.
All of these disciplines interact and inform each other, so if we part some of them out it's still important to have a common identity overlay for them all so that all the practitioners still talk to each other now and then.