Yes, you can send funds outside NZ, but it is a hassle and more expensive. Also, if you are a company, that is sufficiently big so that your bank won't close your bank account down, and you want to accept Bitcoin from online purchasers it is uneconomic to accept Bitcoin as payment. It is uneconomic because it would require you accepting Bitcoin, getting it converted in an overseas exchange to that country's fiat currency and then wiring that money back to NZ and changing it into NZ dollars. Also means that NZ businesses that sell online are missing out on business from people who don't have a credit or debit card, and there are a lot of those out there, particularly in China. (I've been told that only 12% of Chinese have credit cards - on reason why the payment mechanism in WeChat is so popular in China.)