Han people call their fathers "dads" and "dads". Why?

There are some local customs, but there seem to be more people calling dad in the north. I haven't heard much about it in the south.

I don't know, it's basically fortune telling. A friend of mine called him uncle dad, and said he couldn't call him dad. Some people call them by their first names (such as aunts, uncles, first names). . . A bunch of fortune tellers would rather believe it, hehe.