We fathers want to size up the man that may be our daughter's future husband. A boyfriend who is in no way intimidated by the father is one who has no respect for his girlfriend's family, which can suggest that he has no respect for his girlfriend either. A boyfriend who is too entirely intimidated is not strong enough to protect that father's daughter from the many dangerous things that the world has to offer. Fathers are looking for a man who is respectful, but not fearful, who is mature (or immature) enough to talk with the father about items of common interest, but not the false fawning that shows a lack of will.
My relationship with my own in-laws was a bit rocky because we didn't get to meet until the wedding. They had only my wife's word for what kind of a person I was, and as a father I know how unreliable the opinion of a love-sick daughter can be in this area. For that matter, I don't think that I've ever really made a great impression with them as they usually only see me when I'm in my "vacation mode."
I know that I need to be more accepting of my daughters' choices, but I'm acting on a primal level. I need to know that my daughters will be with a person who respects my daughters and our family, that these boyfriends can be depended upon should times get tough, and that they won't lead my daughters down paths that diminish them as persons. I have yet to be truly impressed.
In the mean time, I think that I'll keep having my fun.