1) it's not a window manager issue; applications ought to be responsible enough to create their windows where they want them;
2) it violates separation of concerns; there can be a separate process (such as devilspie) which moves a user's windows around to their heart's content (the difficulty of configuring devilspie itself is not a counterargument to this);
3) it's near-impossible to do well in the window manager anyway, since we don't have any good way in X of recognising that the new window is somehow "the same window" as the old window. Only the application knows that.
Metacity won't fix this because:
1) it's not a window manager issue; applications ought to be responsible enough to create their windows where they want them;
2) it violates separation of concerns; there can be a separate process (such as devilspie) which moves a user's windows around to their heart's content (the difficulty of configuring devilspie itself is not a counterargument to this);
3) it's near-impossible to do well in the window manager anyway, since we don't have any good way in X of recognising that the new window is somehow "the same window" as the old window. Only the application knows that.