Which is not quite the same! "Why don't you just do X?" assumes that the people being spoken to are stupid in some way, overlooking the obvious. "When you tri

Which is not quite the same! "Why don't you just do X?" assumes that the people being spoken to are stupid in some way, overlooking the obvious. "When you tried X, why didn't it do the job?" is a whole lot kinder and doesn't presume that X wasn't tried. And if it wasn't, allows some face-saving and re-thinking.