You're looking at it back to front.
The point is that if it is not an RNAV SID then you need to have all the beacons on the route serviceable, since they are your navigation reference. The same with the VOR approach example.
The fact that you are using your nice FMS to get the a/c along the track is irrelevant, you are supposed to have the raw data displayed to ensure that you actually are following the correct track.
The problem that still exists in large chunks of the world is that modern GPS/FMS systems are
too accurate! They take you to where the beacon is supposed to be rather than where it actually is, and all the flight testing for obstacle clearance was done by someone tracking the real beacon.
So if you are not cross checking the raw data you may be in for a shock one day!
