This isn't a question as much as it is a statement. Mobs seem to spawn at an alarming rate. Simply step left and little after destroying everything, come back to the right and look, another set of monsters hell bent on your destruction. What if mobs were hatched from eggs or what if there was a queen or boss type mob. What if there were a set number of creatures on an entire planet and killing them all won you a bad award.. (Ding!, you just earned the Genocide Badge: Congratulations on completely destroying an entire race of creatures, don't you feel swell) Better yet, what if you could destroy whatever it was that made the monsters spawn thus wiping out that specific species, making your jogs around the world a little more simple. On the other hand, since those same mobs seem to have brothers and sisters underground you will probably never kill them all because of the rapid rate in which they breed. But i suppose the truly ambitious ones could do this. Another idea is future tech, what if an ancient race created some sort of monster cloning lab and released the beasts on the world. This would be fun to try and beat your way through hordes of deadly things to find the tech within the lab they were created in. My point is this, there are so many additional options besides, surprise, a new monster spawned right behind where you just killed one.