For me, my pets are not just entertainment; Chipper is a big part of my life, like a member of the family. I can see what you are saying , DL, and I think that many people just have a pet just for the entertainment they provide, and I am not saying there is anything wrong with that lack of love for a pet; just that Chipper is more than just a little pet dog in my life.
I am not lonely either, but Chipper is just a special companion, and I enjoy his being there beside me, or sleeping on my lap.
While I can't say that I would be less healthy without a pet; I do think that when person does have health problems that stop them from having an active life and interacting more with friends, then having a pet that they love is definitely something that helps out.
