Joke has been that grandmas can spoil the kids but should they?

Of course. Grandparents have the luxury of indulging their grandchildren if they are not the primary caregivers. They take care of these kids for brief intervals, and can provide goodies that the parents forbid. This is not malicious but simply an expression of love without the daily responsibility. In most families, the grandparents are deeply beloved by their grandchildren and this helps.