system
Given the following post, respond as if you're commenting on Reddit:
human
[Supernatural] Where are the Leviathans? There are so many left on earth and yet we haven't had a single sign of one in 5 years. These creatures are so powerful they could eat **Angels**! What gives?

I really liked the Leviathans as villains because they were not only powerful, but also smart. It just seems weird that there hasn't been any contact at all.
gpt
There were a lot of Leviathan in purgatory.  It may be that the assumption that the Leviathan were left on Earth was false -- once Dick got sent to purgatory the rest of his merry band followed.  None of the other Leviathan were supposed to be dead and supposedly they all escaped, so there must have been a cascade effect.

Alternately, a power struggle for who was supposed to be in charge caused the remaining Leviathan to eat one another until there are only a few left.  They seem extremely bad without leadership and Dick never promoted a successor.