Actually I think wobbleblob's reason (because they scare birds and pollute the horizon) is a more prominent reason, I find the Netherlands always quite pretty in comparision with surrounding countries so I'd understand people are reluctant to change that much. Nicer, more colourful buildings, nicer gardens, ... then again it's also a bit boring to me due to being quite flat.
Of course beauty is in the eye of the beholder, but this is really not something I have ever heard before. There are many things to like about living here, but what parts of it are pretty?
- not a lot of ribbon development. That alone makes a huge difference.
- cities of comparable size seem to have more green overall (trees, plants in front of houses, more parks etc). Typical example is something like Ravenstein. Seems to have more park than actual housing area.
- nicer architecture (again, eye of the beholder, but hey we have a 'ugly belgian houses' book :]) for instance streets whith all pretty much the same houses, but every third house has a door in a different pastel color etc. Not sure that even existst here. Or apartment buildings with some color to it.
Of course there also are more ugly things (e.g. there are beautiful pieces of the Waal with nice tiny isles and such, then you look more to the left and there's a rather ugly concrete factory or so; some cities have more 'ghetto-style' places but still not as bad as some parts of Brussles I think). But in general I like it more.
I'd say, for it's size, Netherlands is densely populated.
So depending on where you are you can travel for 150 Km and never leave the built-up areas or you can travel for 150 Km and you'll see nothing but grass, cows, the occasional farm and the highway you're on (A6/A7).
The Netherlands is most certainly not quite average as far as population density goes.