The roads in Holland are simply too small and furnished to cope with a 180 man peloton, especially nearer the towns. It is just too built up and pedestrianised.
Having raced in Holland as an elite amateur I can tell you that the elites have a great way of making it safer. The problem is that there are too many riders, and everyone wants to be near the front. Thus thye best guys hit the front in Kilometer 1, and string everyone out in single file at 60km/h. The crosswinds then break the peloton into more manageable small groups, separated by whole minutes.
Everyone rides like they're on the run all day, and if the front group gets too big, the strongest teams repeat the process until they are happy with the composition of the group.
The pros (esp in stage racing) tend to ride collectively with more consideration for each other, and you don't blow a 3 week race open in the first 2 days....plus there are not many weaker riders in the pro ranks who will get dropped if the speed goes up.