I pay nothing, so I’m obviously not a customer. If Cloudflare decides to stop hosting my site free of charge, I will have to find another host. In that sense I depend on them. Is that what you meant by dependant?
When you pay for a service, you have some leverage with them. You funded part of the service, you're a stakeholder. If they mess up, they lose your business.
That’s arguable. If the free plans help cloudflare grow its brand and customer base and is an effective marketing tool, then it’s helping cloudflare become more profitable. That might make cloudflare a more scalable and efficient business, driving down its costs per customer and enabling lower prices from scale efficiencies.
This is a well known economic effect. I can’t demonstrate it’s the case with cloudflare but it’s quite possible and even likely. Even if it’s not actually driving lower prices, customers can benefit if their service provider is more economically healthy.
I use Cloudflare because it hosts my website for free.