The answer is maybe!
Babies suck for many reasons; hunger, comfort, self soothing and a calming response.
Why do they suck?
Hunger .. sounds obvious but if you just fed your baby then you worry. Did they get enough to eat or did they over feed and now have a tummy ache?
Comfort .. if babies are upset, gassy, tired, having a tummy ache, they will suck
Self soothing .. babies will find something to suck on, paci or fingers
Calming response .. babies sucked their fingers in utero so this is what they are used to