User blog comment:Keekian/The 20 "D" families/@comment-139.179.210.224-20161227054007/@comment-53539-20161227104552

The only reason Ace really had to become a pirate was owed to ancestor shaming. Garp is a Marine, but neither Dragon nor Luffy are... Doflamingo's family didn't feel like World Nobles and him himself was an oddball among his family.

There is some debate on how far ancestry can be used as an excuse.