But it certainly doesn't have to be that way--there's no reason why people can't get more engineering-oriented toys for female children as well, and I'm sure most people who read HN would be more likely to get toys along those lines for their children, regardless of gender.
The issue becomes, then, convincing society at large that this is an issue that needs attention, and that the typical gender roles and toys only reinforce inequality (like representation in tech). That, unfortunately, is difficult, when some (very vocal) people refuse to acknowledge that there is any discrimination in society, and many would think that changing culture around toys is "just being PC."
Such a large change would take a massive effort. While the STEM initiatives going on today, especially those directed at minorities, are a step in the right direction, for them to be effective, I think they'd have to get a lot more mainstream awareness--right now, some people are aware of them, but the majority, in my experience, are not, and even among those that are aware of it, not many a) think it's a good idea and b) care.
Perhaps if a bunch of celebrities got behind it, ads were taken out online and on primetime TV, and politicians started caring? Maybe calling politicians to support STEM initiatives, especially minorities, could help?