Via Palaeoblog there's an interesting paper by a father and son research team out of Finland that considers why life arose. Not why-because-God-was-bored why, but why an assemblage of chemicals on an infant planet became flora and fauna.
The reason is due to entropy. In this case, the entropy being the reduction of energy differences between chemicals on early Earth. It's like when you put a hot object next to a cold object. The hot object warms the cold one, and the cold object cools the warm one until they're the same temperature. Since the sun and the Earth's core were (and are) pumping energy into the system, the reactions between chemicals and the chemicals themselves got steadily more complex until they fit our definition of life. Physorg gives a more thorough description here.
Creationists will go nuts over this because they make two points. One is that life is ultimately a series of reactions that can be described by thermodynamics. The other is that life didn't arise by an event. It became what we describe as life gradually by simple reactions growing in complexity.
In a nutshell, we're here because life was brewed. Like beer.