Using the the apps I have built in this style as an example (not this library in particular though) - starting a whole browser comes with a lot of baggage you may not need - plug-ins as a small example. It’s easier to target 3 OSs than some random permutation.

Also, doing it this way, you can extend the Javascript to add custom callback functions - if that is something you need.

Also, it’s all in one process so there is less fiddly bits (request / response and all that)

You do bring up a good point though, and I hadn’t thought of the PWA angle. It would be an easy way to add a cli interface (just curl I guess)… I might try that next time.