Personally, I think many women are put off by the limited social interaction involved in the job, or at least that's my theory
That turns out to be a myth. Personality test results show women just as likely to score as introverts as men. In fact, in most axis' they are nearly identical. Where they are different (at least on the Meyers-Briggs terminology) is in preference for Thinking vs. Feeling. That's obviously applicable to Engineering.
However, the effect isn't huge. Nowhere is it even 2:1. This is nothing at all like what you'd need to explain the kind of sexual disparity one actually sees in the industry.