Because then you have a ticking time problem. Some automatic service might just silently start failing deep in your tech stack. And yes, you can monitor that. But then your monitoring software might fail, etc.

If you are having a serious (= where failures matter a lot) tech stack, use something that is paid and supported or host it yourself.

I think I see your point, however, what I'm saying is I'd rather pay for something in exchange for some semblance of availability and security guarantees.

That's ok. But I think for private projects something like this is fine. That's why I meant that even if it disappears it doesn't matter.

I would definitely not use something like this commercially.

I think any commercial use of, or reliance on, dynamic DNS is a terrible idea.

If it disappears how do you get a refund?

this comment hit me pretty hard. why do we expect longevity in the free open source world?