The reason is that most of these champions rely on stealth, and whereas pink wards slow down their ganking, such as when Twitch or Rengar or Evelynn flanks someone, placing a red trinket would ruin their surprise/unpredictability factor. Shaco is strong because he can come out of nowhere or juke someone entirely. Twitch can come out of nowhere but puts himself in danger.
AKALI! She would be destroyed by this. A free pink ward right on top of her ruins her ability to wait for cooldowns and outplay opponents.
Kha needs to stealth to get his passive up, Wukong needs his stealth to make strong jukes (his standing still tactic is ruined by this, as well as just plain old W jukes.)
Vayne needs it to make good plays and stay safe, my recommendation for her counterplay is a point and click hard cc like Nauitlius or Pantheon.
Seeing where they were a second or so ago keeps these champions having the ability to do their job with stealth, as well as outplay opponents by either baiting it out, or plain old tricking them with it. If you move in a random pattern while the "stealth detector" goes, then skillshots are very hard to hit.