Question: Why ride for only 8 seconds?
Answer: The 8 second length of a qualified ride was devised purely for the safety and well-being of the animals involved. After 8 seconds the horse or bulls bucking ability decreases because of fatigue, adrenaline loss, etc.
In order to prevent the animal from becoming overly stressed, the buzzer or horn will sound to signal the rider to end the ride and prepare to dismount. This keeps the animals spirit high and healthy and keeps them from 'breaking' or taming down.
The 8 second ride allows rodeo stock to continue competing at the best of their ability at the next rodeo and throughout their career in the arena.