Security. I host personal sites on Linodes and other external servers. There are no inbound ports open to the world. Everything is accessed via Cloudflare Tunnels and locked down via their Zero Trust services. I find this useful and good, as I don't really want to have to develop my personal services to the point where I'd consider them hardened for public internet access.
Then I log in to Linode or whatever and open a hole up in the firewall. That's easy. But Cloudflare rarely goes down, not really something I worry about.
When you have a simple tool you have written for yourself, that you need to be reliable and accessible but also that you don't use frequently enough that it's worth the bother of running on your own server with all of that setup and ongoing maintenance.
The DX is great: simple deployment, no containers, no infra to manage. I build a lot of small weekend projects that I don't want to maintain once shipped. OpenWorkers gives you the same model when you need compliance or data residency.
If your usecase doesn't require redundancy or high-availability, why would you be using something like Cloudflare to start with?