My cat, Smokey, came into my life a few years ago as an adult cat with a huge chip on her shoulder - with good reason.
Our first meeting was at the veterinary hospital. Her photo was on the receptionist's counter. I first noticed her huge green eyes, looking startled. She had been brought to the hospital for euthanization - her people didn't want her anymore. The veterinarian was familiar with Smokey, knew she was a young healthy cat - not to mention gorgeous. She asked the owners if they would turn Smokey over to the vet's ownership. They agreed. When she arrived in my home, I spent the next several years urging her to trust humanity again.
I'll give her previous owners at least one credit - they just didn't throw her out into the street and abandon her life and health to the fates and hazards of outdoor survival. But this is just an example of people acquiring a pet because it looks so cute as a baby animal, but don't consider the commitment of caring for an animal over its lifetime. There is a lot to think about when you decide to bring an animal or bird, or whatever, into your home.
The cost can be enormous if the animal develops health issues. Training is required but often disregarded as too time consuming; but then an undisciplined animal can cause major problems within the household. Having an animal impacts vacation planning, house cleanliness, yard maintenance, grocery bill, health issues if members of the home develop allergies.