Pets

Have I missed something somewhere?  When I was growing up it was not unusual for families to have a dog as a pet.  In fact we had one of our own and it became like one of the family.  

Nowadays though it seems like people have to have three or four dogs if they have them as pets.  Why is this?  Is there some reason why having a pack of them is better than just one?

It must be very congested in a caravan or motorhome with several other animals as well as the human variety.  How do people cope?