You want him to teach you his ways
Growing up comes with the realization that Dad did a pretty damn good job. How did he juggle work, being a husband, and not screwing you up too badly? Show your thanks and probe him for nuggets of life wisdom over drinks. He’s earned it.
You strongly suspect that you’re adopted
Ideally, your parents would tell you that you’re adopted sometime in your childhood, but family histories can get pretty messy and hey, things slip people’s minds! If you want to address the doubts that have plagued you since your parents claimed that the dog ate your baby pics, a drink may help fuel Dad’s honesty. On the plus side, you might find out you’re not gonna inherit his receding hairline.
You need a fixer
Adulthood tends to come in stages, which often coincide with things going wrong in your life. First car breakdown? You need a guy. Legal hurdle? You need a guy. Your dad knows exactly who to talk to, and will set things in motion with an “enough said” should things escalate to new levels of unscrupulousness. Neither your dad nor “the guy” will ask questions -- like Mom would.