Yes immigration policy should discriminate on age

Stuff reports:

A couple who left the United States to live on the West Coast were told they were too old to become New Zealand residents. 

Lisa White, 58, and Dan Butler, 63, moved to Greymouth from Tennessee in 2015 for a slower pace of life. 

It is correct they are too old. Residency is a privilege and given to people who can make a net positive economic contribution to New Zealand. People near retirement age are unlikely to do so.

But their application for permanent residency was instantly rejected by Immigration New Zealand because they were both over 55.
The couple ticked all the boxes in terms of education, experience, character, health and time spent in New Zealand. They could have applied if they had $10 million to bring to New Zealand. 
“That to me is so absurd. You can buy your residency,” White said.

No you can’t buy residency. But having a large sum of money which you can invest in NZ increases your chances of qualifying. Likewise if you are broke, you have less chance of qualifying.

They believed New Zealand immigration policies were written for Auckland, and had no relevance to areas like the West Coast, which needed people to boost its economy. The Coast suffered huge job and population losses since the downturn in the mining industry. 

NZ does not require internal passports like South Africa used to. One immigrates to a country, not a region. People can move around once they are here.