Several things I can think of: "quantity is not quality"; JS developers far outnumber everyone; making web apps look exactly the way they want is easy, and they are not interested in platform-native functionality, preferring a "consistent" UI across platforms instead; "premature optimisation" dogma that means no one cares about efficiency anymore.
Microsoft Teams and (later versions of --- they actually moved away from perfectly decent native Win32) Skype also use Electron, and that's Microsoft. That says the size of the company and its resources matters little in things like this.