One of my DSs had a dummy for sleeping. He was a very unhappy baby, and those dummies were worth their weight in gold. We had a little "ceremony" to get rid of it when he was about two. DS2 never needed one, and fortunately didn't suck his thumb either.
DGC didn't have them, but now we have a four-year-old DGS whose thumb is badly calloused from constant sucking, and who is so far totally resistant to all our efforts to break the habit. What makes it even worse is that proximity of hand to nose when thumb-sucking means that the free fingers on the hand end up there!!!
Three-year-old DGD has never been a thumb-sucker (though she went through a stage of trying it, because big brother does it and she wants to do everything he does), but bites her nails instead!
As others have said, it's horses for courses, and if used sensibly, dummies can be a great thing for both baby and parents, and far better than some of the alternatives, IMO.