Its a local installation, inside the folder, instead on the operating system. Also, other people will automatically install it when the package is saves inside the package.json or yarn file. You can also limit the version you want with these files, that the end user dont need to think about. Just yarn install :)

On top of what others said, ease of use during (team) development through simplicity and consistency - some developers have Macs, some have Linux, some have Windows - and no one wants a work project altering their system anyhow.

I'd like to double-down here on the benefit of having a local installation of a reverse proxy vs what yum/apt gives you.

Though this is the main reason I use Caddy over Nginx. I have my Caddy executable and config for all my projects right there in the home root. I ssh into one of my cheap vps and I'm an `ls` away from remembering how to configure it.

Meanwhile, every time I use Nginx I have to remember where the different folders are that it uses, where the configs are, and how to even start/stop/reload it. I usually symlink its config to the home root and paste a few common commands into ~/README.md for future-me.

Obviously, at a larger scale where you're automating your machines, this doesn't really matter. But at any scale under that where you're sshing into different machines, it becomes a nice to have.

One reason could be that it might be easier for node.js devs to read and understand its source code. I don't use the software nor have read its source code, though.

Sometimes I think that there are not enough of real problems to solve in the js world.

Too many people pumped into a tight space of the frontend development are creating in there another copy of the whole infrastructure while limited by the tools that weren't designed for that.