Porting existig software to JS is advantageous for a few reasons.
NPM makes cross-platform installation simple, easy, and scriptable by default.
Dependency management. The package manager supports both local and global installations, as well as the ability to manage multiple versions of a dependency where necessary. Not by convention, by default. Dependency hell simply isn't an issue in the JS ecosystem.
More secure. Scipt installation/management doesn't require root privileges. The runtime uses it's own sandbox. No matter how safe the underlying OS is, it's virtually impossible for a malicious script to break out and mutate memory/data outside of it's context. PwnToOwn competitions are frequently held to test, identify, and harden security.
Project hosting is trivial to setup. Package installation, upgrade, removal is supported by default.
Scripts aren't tightly coupled to the OS. So you don't have to import the entire universe to use them. For example, Cygwin or MiniGW not required.
Scripts don't require compilation. If you run into problems, it's trivial to open up the source and correct the issue yourself. Shorter iteration/feedback loops on OSS projects means more users are capable of contributing fixes and/or new features.
In short, all of the pain points that suck about native application development have been solved in the JS ecosystem.
Just the 'import the universe' point alone is enough to deter any dane dev from porting a *nix binary to Windows. Disk space isn't the concern, surface area for potential security issues, bugs, and the maintenance overhead of keeping an OS emulation layer updated are.
Javascript is a truly cross-platform solution.