Three reasons:
Traffic
Traffic
Traffic
In many instances, traffic exists as there were no options.
Give people options and what happens?
You pointed out .nl. Take extremely popular ccTLD's like .nl, .de, .jp.
There may be a decrease in traffic (slight, moderate, or large) to the .com once a site is up in those extensions. Notice, I said SITE, not a parked page.
But one of the biggest areas not talked about by anyone is - those sites are now getting traffic the dot com never had or will ever get.
I have not seen any studies in this area. An extremely successful ccTLD site is now getting the traffic that the .com will not get. It may actually be new, un-referred, type in traffic.
In time, I think people in domaining will begin to see things from a different perspective. It is not:
How can an IDN compete with a .com?
It will be:
How can a .com compete with an IDN?
or even a ccTLD.
When I look at the shear numbers of people in China and India, we are talking about billions of people. That is millions of daily searches going on that all of a sudden will be directed/diverted to a native script in Bengali, Hindi, or Mandarin.
Those two countries along have nearly 3 billion people. India is expected to overtake China in population by 2015 thanks, in part, to China's one child policy.
When you combine nationalistic pride with a ccTLD, you have a recipe for success.
When you combine a ccTLD with a government decree that .cn will be the ONLY permissable TLD used by a country within that country, then you have a huge, HOLY COW!
I still maintain my position that I look for China to break totally away from the connected world by declaring its own root servers and having its own internet. There are too many signals that are showing me this.
It's funny, nearly 4 or 5 years ago, people on domain forums were saying to me (in response to some of my threads),
Why should I care what happens in China?
Who cares about IDN's. It'll never happen.
ccTLD's will never amount to anything.
If you just look back for a minute and look at what has happened within the past 5 years, 3 years, 1 year, 6 months, one month ago in terms of technology and internet usage - it is astounding.
Now we are at a tipping point where, instead of waiting for the technology to catch up to us - all these new ccTLDs, IDN's, gTLDs are about to be released creating a very cluttered and competitive space - suddenly it will be technology having to catch up to us (internet usage) to try and sort things out.