To dummy or not to dummy

Until very recently I thought that babies were born already with a dummy in their mouths. It´s been with the babies of a few couples close to us that I have seen that they do not always use or like dummies. What I gather is that dummies are useful to pacify the baby, but other than that they do not have any other particular feature. With almost all babies it works but with some it does not. If the baby likes sucking he/she should have a dummy otherwise he/she will get use to sucking his thumb and when the baby grows up you can always put the dummy away but not his thumb. I have also read around that when the baby starts eating should not use a dummy anymore.