Why is climbing so scary?
Climbing very often puts your body in strange and difficult positions, regardless of the type of climbing. These positions can sometimes be quite scary to be in, especially when including the element of height.
In bouldering, being almost vertical to the ground for certain routes at even a few meters off the ground can be scary, even more so in a sport or lead climbing route, where you may be over 10 meters off the ground.
Many people actually realize that they have a hidden fear of heights that only comes out while they are climbing. The different body positions you put yourself in to climb the different routes adds to the overall fear, and makes the situation that much more scary.