Why do cats come home, but not dogs?

Cats are smarter. And, they use GPS.

Many dogs do return home. But cats are more territorial and tend to stay put in one place whereas dogs wander a bit more. The stray cat that wanders my grandparents property stays. The three stray dogs come and go for sometimes months at a time. They definitely belonged to someone who dumped them because they are friendly and trained! They walk nicely on leads as well. My grandparents tried to find their owners but no one came forward and at least they keep that manky, stinky cat away! 

Because cats are way more loyal.