Due to Netherlands new laws, gambling with loot boxes has become illegal and the government has started cracking down on it. Some time ago, Steam was forced to remove the loot boxes from CS:GO for the region. To avoid the same fate for Dota 2, they decided to make the box content visible before opening it.
However, that doesn’t mean that you should pack your bags and move to Netherlands. Players can no longer obtain multiple boxes at the same time, or sell them on the market. Furthermore, the loot inside the box is tied to your account, meaning that if you somehow get rid of a box and get another one of the same type, you’ll always get the same item. They’ve also left the odds of getting rare items the same.