I've just done the revert - btw you can still add postcodes that you know from your own experience. E.g. I know that the whole of Tekapo is 7999

Or if you know that one paticular street has the same postcode, then it's still worth mapping, because many geocoders are smart enough to infer the postcode from nearby addresses/shops/schools etc. 

For example these search results have a postcode, even though the address node does not: https://osm.org/search?query=11+karamu+st,+akl 