The problem is, this behavior is down to the fact that it's true, you do have to leave NZ to get anywhere in life (for the most part, unless you're happy only hitting it small). The most desirable companies to work for in the technology sector of NZ are essentially Xero and Vend right now, with your other choices being large corporates (Fujitsu, Datacom) or very small early stage startups with small amounts capital.
Startups don't thrive particularly well in New Zealand either, because there's nobody with enough capital to invest in them, so they often don't survive long enough or seek capital from overseas (like Xero/Vend, again, the exception to the rule).
The only natural thing to do is to move to a country with (a) more money, (b) more incentives, (c) more interesting work/problems to solve. The government of New Zealand does little to improve the situation and does not care about the technology sector much, doesn't work hard on getting better internet (we only have one cable to the outside world, and it's expensive to get bandwidth on it!) and doesn't encourage new, young companies to found here.
We just don't have much going for us here, in general, in the technology sector, but it's starting to change with initiatives like this from local government at least: http://hightechcapital.co.nz
It's sad. I wish the government would focus directly on optimizing NZ for technology companies, improve the internet, foster and encourage them (maybe even invest in them), help them get started in the world and meet investors. Some initiatives exist, like the Kiwi Landing Pad, but it's just not good enough yet.