I can see no reason why the circling approach still exists in the 21st century.
Apart from the fact that the circling MDA maybe lower than a normal circuit, the circling approach is no different to an ordinary circuit. There are airline pilots whose career is spent on straight-in radar vectored instrument approaches. Some blame the training environment that shies away from allowing practice circuits and landings in the simulator.
The majority of destinations in Australia are served with GPS. Joining final under GPS guidance may save money, but surely competency at flying a circuit should not be beyond a PPL or a type rated airline pilot. Flown manually, practicing circuits and landings in a simulator is an ideal cost-effective to stay current. It dispels the fear that some airline pilots have of joining downwind for a circuit. Believe me these pilots do exist. Flying a circuit reinforces the basic skills every pilot should have of climbing, turning, straight and level and descending, power changes, trim changes, airmanship look-out, landings and even go-arounds where applicable. All in a relatively short time.
Unfortunately, this aversion by trainers against practice circuits in the simulator may stem from the accent on instrument flying on jet transports. Especially on type rating courses where handling skills on a new type rather than automation are vital for pilot confidence in the early stages of training, practice circuits and landings - particularly in crosswinds - are so important. Once you can fly a decent circuit, then a circling approach is a walk-over.