The free and $20 plan doesn't cover all DDoS attacks. The real stuff costs more than I spend on my entire monthly infrastructure. For my use case, it would cost $6000/mo (I need wildcards and full DDoS mitigation). I'm sure $6k is cheap for someone, but it's not cheap for us.

Meanwhile, providers like OVH, Ramnode, Vultr and BuyVM offer various levels of integrated DDoS protection for their servers and VPS for free or a very reasonable cost ($5-10 per month). It's out there, you just need to look for it.