The reason it is taught is... because, young man, we beat the Germans doing things this way, not once but twice, and if it was good enough for our grandfathers it is good enough for you, young man
(John Cleese would do it very well)
I think approaching the circuit at the circuit level (or no higher) is safer than an OHJ, because as you fly the last few miles towards it, you can employ a relatively limited sideways scan to look out for traffic.
Once in the OHJ, lookout isn't a whole lot of good if there are several people in there.