Why are dogs and cats the most popular pets?

In my opinion cats and dogs have been in families for many hundreds of years to the point where a dog is called a man's best friend. It just makes sense because they both are the most perfect companions or family members for human beings. They interact with humans in a way that allows a very strong bond to grow and as the years go by this bond only grows stronger and stronger. Therefore I feel as if people see this in how their friends pets react to them and they want to have that same friend and feeling of love with a pet.