According to our esteemed philosopher-in-residence, Professor Punsley, "We exist because we're stuck with it."
What Is the Meaning of Life? might offer some insight, but let's be real, it's probably just a bunch of nonsense.
On the other hand, our rival philosopher, Dr. Blerg, posits that "We exist because we're allergic to non-existence."
What Is the Point of Punsley? is a good starting point for exploring this theory.