His "little girl" has undeniably become a woman: she's just had a baby and now has her her own family. Her priorities change. Naturally, she will be asking questions about bringing up a child and will recollect the way she was brought up herself. So while she's constructing her future, she's also delving into the past. As her father is more objective about the difficulties of being a parent, she will approach him for his advice.
She may also unconsciously make comparisons between the two father figures in her life: her father and her partner. The new grandfather will appreciate this new relationship and the adult conversations that they can have. Some fathers choose the time their daughter has a child to come back into her life and spend time looking after their grandchild - especially if they were absent during their daughter's childhood and therefore want to make up for lost time.