They are betting on people don't max out their subscription.
Someone who pays $20 a month may only use 10% of their max budget.
This is true for pretty much every fixed price subscription service in existence
I honestly feel a bit worried Anthropic/OpenAI are going to drop me since I consistently hit my limits
Personally at home I use the free github copilot and then openrouter when that runs out. Last month I used $0.90 of openrouter. Zero so far this month. When my bill starts hitting double digits I'll consider options.
Different matter at work but even there we are paying for API costs and have a monthly allowance (starts at $200/month but increases fairly easy to get)