While It's true that panel lines and flush rivets on an actual painted airplane don't show much, if at all, the emphasizing for these features on a model strangely makes it look more real. I believe that the "flush rivets" on some kits are divots in the plastic to allow a wash. However in most cases you don't see the rivets.
Here are some pics I took at our little local museum to emphasize my point. You can see some panel line and rivets, and others you can't, however, the visual emphasis on the panel lines is not as much as we molders work to achieve.