Because there are different interpretations of the MQOTD by several people.
Here are the rules:
#1: The MQOTD owner can change the rules at any given point.
#2: Guessing the correct title (without expected cheating) will result in 5+ vote* (if the solution wasn't posted yet. )
#3: Guessing the correct title too soon, might be frowned upon by other people. Nothing prevents them from countering the 5+ vote**.
#4: For many the goal of the game is to have fun, not to guess the correct title. If you know the answer and the thread is still short, you might want to wait a while before spoiling the fun.
#5: Witty replies linking to the correct title might also be rewarded by the MQOTD owner and others by a 5+ vote*.
#6: No bashing, flaming, ... on other people.
#7: KSS rule applies, however, quotes sometimes have borderline words, those will be masked by a * as much as possible.
#8: Play fair, do not look it up. If you wait a while you might get a tip from someone else.
#9: Cheating results in a downvote**.
#10: Only the first guess counts.
* Only if upvoting is available. ** Only if downvoting is available.