system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k] Why haven't the Tyranids invented farming?

So, it's repeatedly reinforced that Tyranids only care about biomass. They're not malicious- they don't want to kill people or establish dominance or anything like that. They just want food. They're also clearly a very technologically advanced and intelligent species. Not in the same way a human is, sure, but advanced enough to fight space empires and clever enough for complex galactic strategies.

So why are they still going around eating planets like giant insectoid hunter-gathers? Why not start farming?

Land on a planet, take it over and raise the local inhabitants as livestock. If the local inhabitants are hard to farm for whatever reason (lifespan, breeding rate, solitary)? You're the tyranids. You have ludicrous magic bioengineering. Make them into cows or something. Or just use cows. Kill the people and raise the cows/sheep/blarbles/whatever for slaughter. Use the armies you were using anyway to eat planets to stop anyone blowing up your farm planets.

Hell, just make "cow" swarm organisms. You can make creatures that can fly through space faster then light speed, you can rustle up a cow. Land on an uninhabited planet and let it reproduce. Viola, an endless stream of biomass and I doubt anyone will risk stirring up the Hive Fleet to save a bunch of weird cowbugs.

It seems easy to get a sustainable and reliable source of biomass without the need to keep throwing yourself at space marines every few weeks. It's what *humans* did when we needed a lot of food, and we did it when wheels were the cutting edge of technology. Why hasn't the Hive Mind ever considered the idea?
gpt
I suspect that the Tyranid swarms, much like the Xenomorphs from *Alien*, were originally engineered as a doomsday weapon.  They don't seek a purpose beyond sterilizing a planet to make enough biomass-based weaponry to sterilize the next one.