The option isn't electron vs native, it's electron vs nothing.
The reason why this pattern isn't used more commonly is the fact that right now web browsers simply aren't designed to be used this way unless you start a new instance for just a single app. The second reason is that electron developers are lazy. They only want to test a single browser (or browser version) and are perfectly happy that this means Google can get away with shady things.
Case in point, if I run Slack in Safari, it runs better than the electron version. Functionally, it’s identical, except the scrolling is now native and feels a bit better integrated in macOS. So what’s the point?
(That isn't to say that the web version of Slack isn't horribly engineered too, but it poses far less of a problem)