[sausagefeet]

Curl is a lot more complicated than, I believe, you think. Most people know of it simply as a CLI to hit an HTTP(S) endpoint and write it out. But:

1. It supports basically any file transfer protocol.

2. It is a library that is designed for long running processes.

3. Because it's designed for long running processes, it makes use of every trick it can to pipeline and re-use connections and resources.

4. It has an asynchronous API so it can be integrated into any existing event loop.

Is a web browser or database more complicated? Most certainly, they solve really massive problems. But curl is certainly more complicated than probably most application code that uses it.