The serious explanations I've seen focus on interest more than talent. Women just aren't that interested in programming computers, even when they have the talent (on average, with many individual exceptions).

Programming can be social, though it often isn't. But the basic job is changing machines. While in law the task is to affect people.

In my "things you can't say" speculation, I think the socially awkward guys on the spectrum who dominate the profession are not very attractive for women to be around. Being the only woman in a room full of men can be quite different depending on what kind of men.