This idea changed widely during these days. Now pets are bought for refreshment, to give company, to get fame etc. I have lots of examples for this. Some people may get them for company. They need refreshment after their office hours. Coming to some old people, they want pets in their home to avoid loneliness and some are also earning money through pets by sending then to competitions. Nowadays we can see in news about many competitions for pets like beauty, running swimming etc. Many people want them to guard their house.
Most of all pets are very loyal to their owner. They can be treated as our best friends. We can never expect cheating from them. As far as I consider, they are eligible to be treated like our family