What is the point to functions?

I get the logic of having functions as a whole, like offering at a service.

My issue is the logic in how it’s been deployed. As I understand from the documentation, you test your function inside functions. Then when you’re ready to deploy it to production use, you deploy the function as a app component. So basically the functions service is for development use only.

Why not call it app component testing or something. Am I missing something? The logic seems half baked. Like the idea makes sense, small functions to have and API to send requests to. But how it was built out as a service inside DO doesn’t make sense.