To me, that explains why Etsy has trouble with new tools and languages - they can't hire the developers it'd take to successfully run a project outside of the t

To me, that explains why Etsy has trouble with new tools and languages - they can't hire the developers it'd take to successfully run a project outside of the tools they are used to. Analogously, if you promote by external hiring, you hemorrhage the kind of employee you'd want to promote internally. If you always stay in a particular sandbox, you lose the kind of employee that can work outside it.