The thing is, according to the data we have, it isn't a very lucrative field for women at all, which is what's weirdest to me. One of the things the data cited did was compare 10 year total earnings on average, so for men, engineering compares to an average degree as follows:
Men - Engineering w/ College Degree: $1,845,000 --- AVERAGE College Degree: $1,517,200
So basically, over the ten years after graduating, a male engineer makes about $325k more than a male college graduate on average.
Women - Engineering w/ College Degree: $972,600 --- AVERAGE College Degree: $972,500
A female engineer on the other hand, is barely meeting average. Engineering is literally the single best major out of the ones measured for men, but for women, Business Admin, Health, Math/Phys Sciences, fuck, even Education outperforms it, and Education is atrocious for men.
So basically, a smart woman looking at the data would actively choose not to do Engineering because the pay simply isn't there. If she really wanted to go into a technical field, math/phys sciences will offer her almost $250k more over ten years on average.
I have no idea what causes this disparity, especially given that the other very 'hard science-y' field measured is math/phys sciences, and it's the best paying field available.
If I were forced to extrapolate from my personal biases and my personal experiences, plus the data sitting in front of us, I'd say this (for background, a woman in my family is a very successful engineer for IBM as well, so I'm basing this partially on conversations with her):
All fields suffer if you take a break, but engineering typically offers career paths that get absolutely gutted by time away. They're also incredibly unforgiving about the timing of those breaks - if your pregnancy happens to coincide with the launch of the video game console processor that you're heading up one of the teams for, say... well you're pretty fucking fucked. There's not exactly any way that's going to sit around, and everyone you worked with remembers the extra time they had to put in because of when you happened to get knocked up.
The other fields where women perform well tend to be fields with either no crunch window (business admin does, but it varies WIDELY in structure, so the impact is less, health doesn't really have it at all, and phys sciences has it, but it also has a large academic component which helps pad the numbers out), or outlets that are less reliant on crunch windows.
With no offense intended, I also think engineering in particular has a reputation for being kind of "well prove it" and then ignoring the evidence. As an example, this thread is great - someone presented the evidence, but most of the skeptical comments have as many upvotes as the evidence does, even when they're skeptical comments that were disproved by the very first link.
It makes the conversation feel pretty futile because it makes it seem like if you show up with anything less than ironclad evidence, you get utterly disregarded, and even if you bring ironclad evidence, 95% of people will ignore it. Sure, you're talking and engaging - but how many of the 55 people who upvoted you paid attention to another comment in this chain? I'm gonna get 5-10 upvotes, so will you. Most people read that first post, read your rebuttal, and then dismissed the first post as bullshit and moved on.
Engineering is the field with this reputation, and deserved or not, I think it has a serious impact on how many people go into it.
When I was choosing my major, I had several options and I specifically chose not to do engineering in part because the cultures of the engineering schools available to me was unappealing at best.