In temples it is a customary practice to undertake rituals to ward off evil eyes towards Perumal; after Perumal returns to the temple after his ceremonial processing in the streets, he is placed in his sanctum after undergoing ritual to ward off evil eyes. To this day, this can be witnessed at many temples. Similarly, it is a practice at homes for elders to ward off evil eyes related to youngsters.
A prapanna need not fear the ill effects of evil eyes, but an absolute faith that Emperuman will protect is a must. All the practices to ward off evil eyes are in place to remind us of the absolute faith in Emperuman that he will protect us. It appears the elders follow these practices to reinforce the faith in Emperuman as our protector.