I understand that occasionally, the clues are longer than normal even if the players are right all the time, but in particular, it's when a Daily Double remains hidden, meaning the lack of a key turning point in the game, and especially so since late in the round is when a Daily Double can be the most important.
On Wheel, it's when any contestant solves the puzzle with less than $2,000 in their bank and there are still uncovered consonants, plus it isn't a speedup or Prize Puzzle. Considering how important the Prize Puzzle round is in addition to the tossups, solving for such a modest amount isn't going to help in terms of winning one bit, and you're guaranteed $1,000 just for playing. Also, solving early during the Express and solving during the speedup without picking a letter first.
Sometimes, though, contestants believe in the old "slow and steady wins the race" adage. There was -- supposedly -- at least one WoF contestant, possibly during the Woolery era, who swept the game, and solved each puzzle so quickly they were able to play (at least) five rounds ... back then an extreme rarity, even without the Bonus Round. No telling how much money he had in any of the rounds, but the fact was he won -- solving as soon as he thought he knew the puzzle -- and got to come back another day.
And remember, there were many contestants who could have continued spinning and had tens of thousands of dollars in their bank, but wisely stopped as soon as they thought they knew the puzzle. The best example I can think of was the woman who solved a puzzle with $27,500 in her bank with less than half the puzzle -- DUE TO CIRCUMSTANCES BEYOND OUR CONTROL -- revealed ... and won two cars. Thing was, she could have spun on and found several multiples of letters in the puzzle, and possibly built a $40,000 or $50,000 bank (and won more than half of the stated value of prizes available on that episode) ... or she could have landed on Bankrupt or Lose a Turn and someone else cashes in with just a few hundred dollars.
Brian