Why We Like Diminutives: Doll turns into Dollie, Dog goes to Doggy

A 'diminutive' is something you stick on the end of a word to make the thing it describes sound smaller. ie. Dog goes to Doggy. Every language has them, but some have more than others. Why are we drawn to diminutives? And why is English particularly resistant to them, compared to Spanish, for example? Here's a 'little' about the subject...