Dimples are the side effect of how face muscles have formed !!!
They are not there for anything useful.
About 20 - 30% of people worldwide have dimples.
Why do we get them ??
When our face was forming in womb, one cheek muscle got bit shorter or split.
So when we smile, this shortened muscle pulls the skin IN a little. This makes the dimple.
So, in simple words
SHORT MUSCLE + SMILE = DIMPLE !!!
Dimples tend to run in families. It is because of genes.
If parents have dimples, their children are more likely to have them.
Dimples don't have any specific useful work to do !!!
They are harmless and people often find them " CUTE ".