See:
Nemesis, when the Scimitar directly hits the viewscreen and the front of the bridge is blown out. In that and Voyager's "Year of Hell" the view of the enemy ship through the breach is the same as would have been on-screen, had the screen still been there.
I've always seen it as budgetary/fx contraints or hope-they-don't-notice-itis that they never showed the saucer from the bridge or observation lounge behind. Especially annoying for me was the Obs lounge on the Enterprise-E, which should have had an incredible view of the ship, which we only ever saw properly in the Elite Force II videogame.