Yeah, and who says there has to be a why????
Seriously, 'why' suggests volition, intention. If a light bulb burns out, is there some volition behind it? If If a child dies of leukemia, is there some volition behind it? If there is an earthquake, is there some volition behind it? If you've answered 'yes' to any of these questions, how do you know there is volition behind it?
The action of a light bulb burning out is very different than a chimp stripping the leaves off a branch and sticking it in a termite mound. There is volition involved in the second action; there is intention. Just as there is intention when we throw a spear at an antelope, or hit a baseball, or type on a keyboard. There is no volition when a light bulb burns out, or when an atom decays. There is no volition behind the universe. It exists. There is no reason it is here. There is no 'why'.
No one decided the sky should be blue.
Dan Dennett has discussed in various places how our ability to predict the actions of other conscious beings like prey or other people has led us to look for intentionality where none exists. Kinda like over-generalization in language learning. Useful, but it can be taken too far. Pattern recognition is another one that the religious like to take way too far.