Because of people like this. Or the person (or people) who thought it would be fun to put cats in a bag and beat them to death, or the guy who raped and killed an 11-month old.
Umm....look, I think beating a bag of cats to death is horrific and all, and certainly the product of a disturbed mentality, but beating a bag of animals to death isn't in the same ballpark as rape and murder of a person. With the animals you're looking at a psych eval and if that passes then 5 years prison time (maybe) for cruelty to animals charges.
In good sci-fi literature we see this come up again and again in many hypothetical scenarios. Ian Douglas answers the Fermi Paradox by positing a future where a galaxy-spanning race of hyper-darwinist xenophobes mercilessly wipe out any space faring "other" race much to humanity's horror when they stumble across ruins, relics, and artifacts left by other races.
In the Crystal Spheres by David Brin we see a future where all intelligent life is closed off from habitable worlds until they themselves become space faring, and humanity is among the first to reach the stars.
In To Outlive Eternity by Poul Anderson we see a possible scenario in which humans are first by design.
Peter F. Hamilton takes us through another possibility in the Night's Dawn Trilogy where intelligent life is fairly rare and what there is out there doesn't really have an interest in "lesser" forms.
In all, we won't know for sure for a long while yet, but I think there are some good possibilities out there. And until we actually do make contact or prove ourselves to be alone, good sci-fi keeps us company in the meantime =)
Few programmers actually do sorts and list manipulation at that level anymore, but any of them worth a damn should be *able* to do them at that level and understand the underlying theory to make the most effective use of them.
You may not need to be a mechanic to drive a car, but you'll damn sure get better performance out of it if you are.
"More software projects have gone awry for lack of calendar time than for all other causes combined." -- Fred Brooks, Jr., _The Mythical Man Month_