There are many reasons why developers use Electron for GUI development. The size of the final package is not very important, and creating many times the same native application is not that appealing. Having a cross platform, responsive, and a modern high quality framework is much more appealing.
You can only install so many packages with this philosophy before size starts to be important after. More to the point, you can only run a few of them at a time, on machines with gigabytes of RAM. This is a profound embarrassment to our industry. If by "responsive" you're referring to input latency, Electron apps are at best on par with native, usually worse IME. If by "responsive" you mean accommodating different displays... it's a desktop app. Your statement about a "high quality framework" is basically orthogonal to reality, but I'd like to see you justify rating React "higher quality" than Qt5.