Rainboe,
Different markets. You won't fill an A380 between Los Angeles and San Francisco - so NZ are right to put a 777 on that run - but you will fill an A380 between Singapore and Heathrow - so every man and his dog who is planning to, is right to run them on that run. Likewise you'd be barking to put anything bigger than a 767 between Manchester and New York.
To say that those running 767s and 777s on the same route won't be able to compete with A380s on the same run - that's a generalisation which cannot stand up to examination. Some carriers' business models will prefer one big run a day, whilst others will offer smaller aircraft more frequently. Under your logic, for example, KJFK-EGLL would today be run almost wholly by a smaller number of 747 runs. Instead, we have all the ex-EGLL carriers crowing about their frequencies - some of which are 747, but many of which are not.
Certainly there are some high-demand routes which will stand multiple A380 runs per day (eg. EK London to Dubai, which is why EK are buying 45 of them - and let's face it, it's not that big a leap from there to 50 airframes, which I am sure EK have in mind... ).
For others, it will be a chance to cut costs as if you do want to move 500 people a day from A to B, then it might be cheaper (considering landing and nav fees, G/H charges, etc.) to do it all in one big hit than two smaller airframes; but in doing so, you give your customers less choice in scheduling than with two flights. So horses for courses accoring to your business model and target market.
Whether one likes the look of the beast or not, there are some routes which will support an A380. Whether the manufacturer has over-estimated the number of such routes, only time will tell. We can argue about it all we like, as an EU taxpayer I hope it works so that my tax input (in whatever form) hasn't been wasted and I put a level of trust in all the EDHEC and INSEAD graduates crunching the numbers in Toulouse that there is a business case for it. It's called 'risk management' and every business does it in one way or another.