This is a very important question. The demand for pets determines the supply. Many people can see the use of keeping cattle: they serve as food for people. But what use are pets? The most common reasons for keeping pets are:
company
socializing
they are beautiful, nice and interesting
status
something to do
Company
Many people have pets to substitute relationships with partners, children or family members. Many elderly people for instance, like having a dog instead of being all alone at home. This is usually a lap dog, very affectionate and strokable.
The animal serves people's need to cherish, love and fight boredom. But this is really a distressing reason for keeping a pet. The animal is a replacement for normal human contact, something that apparently is too much to summon in our individualistic society. Their pet keeps them from pining. But of course, it has to be a type of dog that suits them and that has been bred especially for their needs.
Socializing
Pets make socializing with others easier. People are more inclined to start a conversation when they can focus their attention on the animal in a moment of silence. Just like with any other hobby, it's nice to talk to people that have the same hobby.
