system
Given the following post, respond as if you're commenting on Reddit:
human
[D&D/Pathfinder] Why isn't the world full of ancient dragons?

Think about it. Dragons are portrayed in both flavor and statistics as some of the most powerful creatures on the Prime Material Plane. Even a newborn outmatches the vast majority of human warriors, and is also a reasonably intelligent and extremely haughty and greedy creature. And with age, dragons only become larger and more cunning and powerful.

So why do so few dragons reach their maximum age? Why would the vast majority of them die before they reach maturity? Why don't dragons dominate the world? There surely aren't enough seasoned adventurers running around to kill off almost every one of the ~35 types of dragons with full age progressions that have been published for Pathfinder.
gpt
1.  Dragons are very territorial.  They hate each other generally, and vie constantly for resources.  Any given million-square-mile area is unlikely to have more than one ancient dragon; lesser wyrms may be tolerated, but as they grow in power and age the eldest will come for them.

2.  Dragons are *very* powerful, but not invincible.  They are a threat of a magnitude sufficient to unite many other entities against them, and they're arrogant enough to rarely think they need their own allies.

3.  Dragons don't mate and lay eggs often.  Once every few hundred years, most likely.  That's not a high birth rate.