Why do we keep cats, dogs, birds, snakes?
I can also tell you that if you believe that the cattle that we breed to eat and milk, are not genetically altered through the years then you are making a mistake.
The milking cows have been developed into milking "machines",
and the one we slaughter for meat (at least the ones that are more profitable) look like body builders. Excessive mass, no fat etc. I know, this is what I do for a living.
The same thing applies to chiken, lamb, fish, even vegetables....
In reality, you cannot feed billions of people on this planet without some fooling around with mother nature. Hey, we even alter the routes of rivers etc... Have we any clue whatsoever to the changes these actions may bring in tens or hundreds of years?
I just think that the ethical dilema here is should you fool around with mother nature just for fun.... Simply does the cause justify the means? For feeding the masses cheap food some may answer yes.
It is not an easy subject to debate.....