I'm not sure why it makes you sad. On a germane-to-the-parent-comment sense, that's pretty much exactly what tptacek said. But on a wider scale, if you are trying to help someone, wouldn't you want to give them advice that truly helps them in a big and cross-task way? Much better than "get good at Rails", which is useful only for a subset of engineering roles (albeit a subset I may enjoy). In terms of time investment... you can get pretty okay at sales in the time it takes you to be as expert as is potentially relevant in Rails. So why not choose sales?