Extremely durable, fast growing, highly disgusting source of protein?
EDIT:
GPT says:
Because, disturbingly, cockroaches are actually useful livestock.
The biggest reasons people deliberately raise millions of them are:
Animal feed. Roaches are cheap, protein-rich food for reptiles, fish, birds, and some farmed animals. They reproduce rapidly and can be raised vertically in enormous densities.
Traditional Chinese medicine. This is the really surprising one. China has had industrial-scale farms raising species such as the American cockroach (Periplaneta americana). They are processed into extracts used in some traditional/approved medicinal preparations, particularly products marketed for wound healing and gastrointestinal conditions. Evidence varies considerably depending on the claimed use.
Waste conversion. Cockroaches will eat a remarkable range of organic waste. A colony can convert food scraps into insect biomass and frass, somewhat like black soldier-fly farming.
Research. Their nervous systems, regeneration, microbiomes, disease resistance, and extraordinarily robust immune defenses make them useful experimental organisms.
Pet/feed market. Dubia roaches in particular are commercially raised as feeder insects. Compared with crickets, they're quiet, don't smell nearly as much, live a long time, reproduce reliably, and can't climb smooth surfaces.
Supposedly there are some Chinese farms with literally billions of roaches.