Somewhat agree. Dropbox didn't sell because it had shiny icons for folders or sexy web interface. It sold because it provided immense value and it just worked. Same can be said about Google, YouTube, Microsoft Word etc. None of them had sexy design to start with but they simply worked and provided great value to end-users.
You've picked apps with necessarily minimal interfaces; the only exception being Microsoft Word. Word doesn't need a new UI every other year but it gets one because, without making the UI sexier each year, people don't buy it.
