Board Thread:Naruto Discussions/@comment-26894845-20150816232558/@comment-26518343-20150823120512

Two reasons.

1. Considering the power of the enemies that are introduced in Shippuden (Akatsuki members and Madara), Rock Lee getting drunk or Kiba's dog eating food pills wouldn't have made a shred of difference in those conflicts.

2. In the case of Rock Lee and Kimimaro, it was a mission with a bunch of genin and no Jonin to back them up. Logic says one or more of them should have died. There had to be a viable way for the group to hold off Kimimaro without every last one of them being murdered during that storyline. Thus we see Rock Lee's drunken fist. Also explains why Kimimaro was terminally ill. Having him be weakened supported the idea that a group of Genin survived the mission intact.