You know this actually is a valid scientific question. And vets do have a degree in animal psychology, though I haven't asked one yet. When I pet my animals and stop, they look so disappointed. We even had one, Fluffy, who would try to grab your hand back. How many pets psychologically speaking does your pet need each day? I have found that twenty a day seems enough. What do the rest of you think? And has the matter been studied scientifically?
When you take an animal away from it's natural environment and keep it in your home, it needs to be treated as part of your family. Over he years, I have never had trouble with animals, mainly because I brought our children up to treat them as living creatures, rather than toys. Being independant, cats are much easier to look after than dogs. Some people are just not capable of looking after animals and treating them as individuals.
I think it really depends on the animal and what their preference is. I have had cats that wanted to be with me all the time, would lay on my back as I slept even and I have had others that rarely wanted to be pet or just tolerated it. I have a cat now that insists on going everywhere with me but doesn't want to be held at all anymore, even though when he was smaller, he loved to cuddle. He doesn't mind getting pet but he rarely seeks it out.