What do you find stupid? The way I see it, HTML/JS is a pretty good higher-level GUI language, and much effort has been spent making it work well. The overhead is worth it if it makes developers more productive.
Is it? The costs which you offset with developer productivity get multiplied times the number of users, which is orders of magnitude more than number of developers.
And value delivered also gets multiplied by the number of users. VS Code users decided that they like it even after accounting for Electron. Clearly, then, VS Code has certain strengths, and I'd argue that some of those strengths are made possible by Electron. Second, great design requires experimentation, and Electron makes it easier to experiment with editor UI. VS Code could become a place to prototype ideas that eventually improve your more efficient editor.
Why I agree on "much effort has been spent" it is very hard to agree about HTML which was meant to be used for marking up static documents combination with ad-hoc scripting language being "pretty good" for GUI. More like "possible to work around a bit".
They will indeed fix this. At minimum, they can freeze the editor when it's out of focus. So there is no need to justify--this is a minor oversight, as someone phrased it over at Slashdot.[1]
I was responding to those who believe that this demonstrates a fundamental flaw in using Electron. My response emphasizes the tradeoffs involved. If they couldn't fix it, 13% background is undesirable, but it's not a dealbreaker for me if there are redeeming qualities. And it seems that VS Code certainly has some redeeming qualities.