There are many ways to safely and appropriately travel in the backcountry. In areas with well marked trails, a clear destination it MAY be safe to go without even map and compass. However even in these areas there are uncertainties "things can happen" that can get you lost. Perhaps you wander to another lake to fish, perhaps you see a peak you want to climb, perhaps there is a use trail heading in a similar direction to the "real trail". Any of these can get you lost even though you're theoretically on trail. A map and compass and/or GPS can help get you found.
Even in easy navigation situations knowing where you are on a map is the best way to stay found. I agree that a compass or GPS is rarely needed.
If you travel cross country, on any longer trips, or through complex terrain a more detailed map is needed. I've traveled cross country with low resolution maps both after establishing and marking a route that "should go" and by just using what I could see from the field. The latter technique introduces more uncertainty and can result in delays and traveling over more complex/difficult terrain than you intended. In all of these situations a compass and/or GPS can be essential to "stay found" and plan routes.
Another reason to have more detailed maps is being able to adjust your route on the fly. I've had group members become sick and had to get them out over cross country routes I hadn't planned on taking before I left. In these cases detailed maps and bombproof navigation is critical.
In comparing the compass with the GPS both have advantages and disadvantages. A compass works in heavy trees (at least for establishing a bearing of travel) where a GPS won't. A compass doesn't depend on batteries. It is probably less likely to become non-functional in the field. A GPS will tell you where you are without triangulation and in poor visability.
It's important, like with all our gear, to consider the conditions you're likely to encounter, build in a safety margin, and take the gear you're likely to need. On a well marked trail, a map may be enough. On cross country routes especially in winter (trails burried, potential for dense fog/snow) maps, compass, and a GPS may be needed.
I'm not so sure that we'll ever look back and laugh that we ever used compasses. The tendency of our society has been toward increasing specialization and fewer individual skills. I'm not sure this is a good trend. Backcountry travel for me is a way to regain complete responsibility for my life. Certainly GPSs can make travel easy like cars make travel easier. However I fight against relying too completely on both. I don't want to lose my ability to walk as society develops more ways to transport me. I'd also hate to lose my ability to dead reakon or navigate by compass. In fact I'm hoping to move the opposite direction and navigate with lower resolution maps and be more in tune with the conditions in the field.