What it shows it that the son grows around the sport, has a father who is able to teach it to them, and grows up to emulate their father. How is that any different from Peyton Manning, Brian Greise, Jarrot Payton, or any number of NFL players who grew up watching their father and followed in his footsteps?
And the skill to play any sport is attained through experience.
The difference is there are over 1500 slots to fill in the NFL, a lot more oppurtunity for a son to perhaps grow up and attain a spot similar to what his father held. Nascar has 43 slots, and they are routinely nailed down by Petty's, LaBonte's, Allison's, Earnhardt's, etc... Really tells on itself.