There is a simple reason. As we all know, medicine is used to treat diseases. On the surface, giving medicine is giving health, but who will give medicine to others when the other person is healthy?
The original intention of sending a longevity lock is to hope that she will live a long and healthy life, but besides wishing the elderly a long and healthy life on their birthdays, who else will wish others a long and healthy life? Wishing you a long and healthy life shouldn't be a greeting when you meet, should it? !
In addition, there is a clerical error in your relationship with your junior. If it's an uncle, it should be your niece. On the contrary, if the other person is your niece, you should be the other person's uncle or uncle.
I hope I can help you.