I think keeping a pet shows our need for companionship and quite possibly our need to be loved un-conditionally. For some it's a sense of ownership and power.
I agree VI - pet ownership serves different needs for different people.
I have a friend who has a dog, and he certainly loves his dog, but he also takes great pride in showing his dominance over the dog. The dog listens beautifully to any command it's given... and comparatively, my dog is a wayward mutt that listens to little more than the sound of kibble landing in his dish... but I find myself feeling somehow more rewarded to have his company by his own choice rather than through a command to "come here". He will listen if I use a particularly stern voice to some basic commands, but I find myself loath to do so unless it's an issue of safety.
It's actually disturbing to me when I see pet owners treating their animals like objects to be ordered around to the point of being told when to sit, stand, pee, lie down, move, don't move etc. This seems to me more an issue of power and dominance than mutual companionship and respect.
I know there are many dog owners out there who would disagree, and their dogs would certainly put mine to shame in the obedience department, but considering my dog was a cowering, frightened pup that already showed signs of abuse when I got him, his 'not listening' to me now tells me I've restored his self confidence and sense of personal safety. This to me is far more important than having a dog that sits pretty upon my whim.
ah.. ooops... I may have digressed - perhaps this ought to go into the off topic thread. lolll