SaltyNZ:
EDIT to add - and you already pay tax on dividends from shares and income investment returns on Kiwisaver. Arguably you should also pay tax on the capital gain on the shares when you sell or borrow against them too.
You're not correct regarding Kiwisaver. You are taxed as if your Kiwisaver is generating gains, even if it isn't.
https://www.stuff.co.nz/business/money/132893837/the-capital-gains-tax-you-dont-know-youre-paying
Tax is hugely detailed and it amuses me no end that having just been through a pandemic where the over-riding message was "trust the experts", people have zero qualms about making misleading, disingenuous or plain incorrect assertions about the tax system.