Originally Posted by https://www.engadget.com/2010/01/13/drop-chance-probability/
If your mount has a 1% chance of dropping, it will always be 1% on every single attempt. The Gambler's Fallacy trap that many fall into is assuming that previous results will change future results -- or put in WoW terms, "I've run this 50 times, so it must be really likely to drop now!" And it really feels like it should be that way. But it's not any more likely on the 50th kill or the 500th kill, it's still 1%. Every. Single. Time.