The Press appears to be mystified as to why this should be so.
The reasons for this schemozzle are simple and unpalatable.
1 - The bureaucracy running things in the Old CBD has no notion of Time=Money. A building proposed in 2011 for $30m will now cost $40m (construction cost inflation runs at around 8-12% per annum).
So the pure elapse of time renders proposals unfeasible by the time the final box is ticked.
2 - The New CBD ( (Sydenham/Addington/Middleton/Riccarton/Hornby/Airport arc, plus the Oxford Terrace to Bealey Ave strip and Montreal/Victoria Street) has forged ahead, safely out of the cold dead hands of CCDU and CERA, and has thereby taken most if not all of the potential business tenancies.
Just as Selwyn DC's IZone has eaten CCC's industrial-land lunch, the New CBD has eaten the Old CBDs'. And even there, vacancy rates are not zero: there is plenty of $300-ish per square per year floor space for rent...
3 - The Precincts are too big. Getting tenants for a single existing New CBD floor plate is hard enough now at $300-400 - try getting an entire blocks' worth at $600-700 in the Old CBD.
If CCDU and CERA had read their disaster history (great Fires in London, Chicago) they would have realised that individual owners drive regeneration. Not city-block-size behemoths. So the Baron Haussmann fantasies are just that - fantasies.
4 - Share-an-Idea placated the masses by seeming to promise their 'input', and disguised the ineptitude that actually existed. It also promoted an absolute fantasy that building design and contract commercials could somehow be democratised. This accounts for much of the later disillusionment with planners, schemes, precincts et al.
Buildings need haggle, tenants, financiers, and persistence. Not one soul per 10,000 who Shared their (often hilarious) Idea had any skin in the game except as a passive consumer of whatever eventuated. A total failure, yet a useful circus act.