A couple of others I can think of:
- Crypto-boom of 2016ish: GPUs/mining rigs
- LLM/AI hype nowish: User generated data
- 90’s dotcom bubble: Server space
Delivery services and rideshares. People using them make meager wages, but the companies hosting them get all the benefit of people desperate for work or convenience.
Edit: in a similar vein, OnlyFans