Stress. I have it, you have it and chances are even your kids feel it. To deal with stress, most people self-soothe and learn a coping mechanism. Some people smoke, some people run, others takes medicine. I notice that I have quite a few soother habits, I bounce my leg or twirl my hair or chew the inside of my cheek.
Some Autistic folks develop quite the arsenal of self soothing exercises...some spin to center themselves, some flap their arms, some repeat words, numbers or phrases. People with OCD have their own unique quips for dealing as well.
Babies and toddlers have ways to deal with stress themselves...crying, sucking, nursing, sleeping. Babies who nurse get their non-nutritive sucking needs met by suckling the breast. That's how they seem to best get their stress dealt with. Bottle fed babies sometimes go for thumb or pacifier sucking to meet that need. Other kids hold blankets or dolls.
The point of this post is to get you to look at pacifying and thumb-sucking and non-nutritive nursing in a new light. It isn't something for lazy mom's to use. It isn't something kids use as manipulation. It starts out as a reflex, that is found to be quite soothing and stress relieving. Most kids stop using a pacifier between 2 and 4 all on their own. Most kids stop sucking their thumb between 4 and 6 all on their own. A great medical postings on non-nutritive sucking and why it's normal and ok. HERE and HERE . Did you know that thumb-sucking and pacifier sucking releases endorphins(the feel good hormone). Yeah, that's why it is an excellent tool for babies to cope with stress. Sucking starts out as a reflex that develops into a tool.
So, before you dismiss baby's need outside of food or even your toddlers need, remember. It is a not a bad thing. It is healthy and natural. And for the most part...most kids give them up on their own when they are old enough to understand and deal with stress in a better manner.