Why does a vast majority of children in Haiti suck their thumbs? How do their parents handle that?

I do not know why.  I've read that it's a behavior that soothes them.

Some of the kids I hanged with, in Haiti, sucked their fingers.
Some children suck their thumbs, some the index and middle finger together,
and others suck the middle and ring fingers.

A lot of these children retain that behavior well into their puberscent years.

The remedies that I have seen parents use to help them break this habit are sometimes 'unusual'.
The most common remedy was to rub freshly cut bitter aloe unto the child finger.
Other parents would bandage the child's finger during the night, since a lot of kids suck their fingers while sleeping.
Some parents would smear chicken poop onto the child's finger in the hope that he/she would find that finger repugnant.
Some parents took this fight even further and would threaten to stick the finger in boiling water.
I have seen one father take a machete, had the child put her fingers on a piece of wood, and threathened to cut the child's finger until she promised that she wouldn't do it again.  That girl did eventually stop this behavior on her own.

Creole definitions:
suck thumb, suck fingers - tete dwèt, souse dwèt
Does he suck his thumbs? - Eske li tete dwèt?