An even better reason would potentially be security. Exploits in electron are pretty common, which may be a result of its ubiquity making it a big target. But also it's just a complicated platform to secure.
And from your other comment
>we in the Slack Desktop team
Seems misleading to declare something like this without a disclaimer that you work for the company in question, especially when phrasing it as if you are definitively not a part of said company.