The thing that's big about Electron is it allows web developers to use their existing skills to create desktop apps.
A lot of web developers would like to make desktop apps, but aren't willing to learn a new systems language to do that, especially when there's a solution that lets them use the JS + HTML + CSS they already know.
Also it lets you reuse parts of your web app (or build part of your web app while building your desktop app). For something like Slack, or if Google were to make a desktop version of Docs, it makes a lot of sense to use Electron because you already have your web app and you want your desktop app to be consistent with it.
I've used Ionic with a very small team to make a web app and mobile app from the same codebase. The client asked if we could also make a desktop version for them, and instead of taking months to build one and make it consistent with the web/mobile apps, it was just a few days of learning to wrap it up with Electron. That was really neat!
And the beauty of Electron is that you can still write all your actual logic in C/C++ and use Node's FFI to bind it to your UI.
(Qt is transitioning to the same model with its HTML+JS based Qt Quick orchestrated from native code; but it's far less production ready than Electron right now.)
A developer that only knows js is unlikely to be competent (beginners aside).
Oh, don't get me started…
Yes, that's a problem. But Electron can hardly be blamed for it. They'd use XULRunner if it didn't.