Because 7 was a 6 offender.
How many dragon Ball z characters does it take to screw in a lightbulb? Only one, but it'll take at least 6 episodes!
Because in charge of directing, Yoda was
He puts down the three and carries the one.
Hey Microsoft, why is there no Windows 9? You've given us 7 and 8, and now you're skipping straight to 10?" "Well, to be completely honest, 7 8 9."