“I’ll care for you, love you and even provide for you, but ultimately I’m in charge and what I say goes. So in short: daddies tend to be older and, more often than not, on the dominant side.
The trope is an identifier for older men, but also a label that’s often put on them by younger guys whether they like it or not.
Depending on the person it can be a kink fantasy, or a genuine relationship philosophy.