The first time you open a .desktop file that's *not* on the Plasma desktop, you see a dialog window asking you if you want to launch the app or edit its .desktop file. The dialog also contains an "always do this in the future" checkbox. When the user clicks this checkbox amounts, it amounts to them trying to predict their own intentions in the future, inviting errors. For example, in Bug 512378 a user clicked that checkbox and then the "open in Kate" button, thereby ensuring that .desktop files opened from Dolphin never launched for them ever again. The user forgot they did this and assumed the behavior of opening in Kate was a bug. The UI to change this decision is in Dolphin, which we can't guarantee is installed, and where the user is not likely to know it exists because they didn't access it from there.