Because the market is tiny. Recruiters can't specialize, and those that do get eaten up by the likes of Datacom or Australian-based providers.
Most recruiters in NZ start from labourer/contracting/HR firms and then move into tech because it's better paid. Whereas in Australia you get people who trained specifically to be a tech recruiter, or migrated to recruitment from tech (usually BA and QA type roles).
Safe to say the quality of tech recruiters in New Zealand is even lower than those elsewhere.