Why do babies dribble when they are teething?

Answer 1

Quite simply, during the daytime, the baby is likely more engaged with and distracted by things going on around him or her. Even though the baby might still feel some of the discomfort or pain, there are enough other stimuli to shift the baby's focus. At night, those outside stimuli aren't present, and the baby has no distraction from the discomfort of teething. In addition, a baby who typically sleeps through the night but then wakes up from incoming teeth becomes frustrated over the inability to sleep and fall back asleep. This might make the pain more acute, the frustration may increase, and an unpleasent cycle of nighttime crying while teething might ensue.

Answer 2

Because it hurts when the tooth breaks through the gum.

Answer 3

If you mean why do they drool it is probably because their lips are not big enough to close around their teeth so they drool.