Because 7 8 9.
Because 7 ate 9.
They don't have Windows installed.)
28 29's
Because he never existed.
Nothing because ghosts don't exist. Edit:Holy crap I just realized I didn't post this on /r/antijokes.
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."