The tops and the flats of drop bars should not be used unless the road ahead is clear, and sight is good. With the riders hands in these two positions, they do not have immidiate access to the brakes, which is why most cycling clubs and organised group rides stress that these hand positions are not to be used when travelling in close proximity with other riders.
The tops are most appropriatly used for spoiling a headwind for riders behind you, and for in the saddle climbing. The flats are most appropriate for fast cruising, especially over bumpy or winding roads. The rider must be aware that they are unable to reach the brakes immidiately, and so must take this into account when placing their hands in either of these two positions.
That means that the tops and flats are innapropriate for most city commuting situations, leaving the rider to choose between the hoods and the drops - where access to brakes is natural and unrestricted.
I take your point about inexperienced cyclists, but IME with inexperienced cyclists using a drop bar bike, they are very reluctant to move their hands away from the brake anyway.
I personally believe drop bars to be perfect commuting bars - they allow a number of different hand positions, they are very narrow and they allow a more aerodynamic positon.