There's a good reason why people used to use 50mm for learning photography. In older days, most camera are manual and there's no zoom. 50mm is commonly available across all manufacturer as it is the most natural perspective (same as our eyes) and thus pleasing. Also, but using a standard lens, you learn to maximise the usage by stepping closer, shot from high angle (imagine bird photographers climbing trees) etc.
With digital photography, 50mm becomes 75-80mm and may not be so useful as the perspective is not quite right for photo-journalism etc. However, it may be a useful lens for portaits as portrait lens usually range between 85-120mm and most people owns a fixed f2.8 105mm will find it more difficult to use the lens.
Of course, i do own the 18-70mm which the 70mm is perfectly ok to use as portrait as it becomes a 105mm! there's a good reason why nikon choose 18-70 as the kit lens vs the 28-120 VR as it will not be so useful in all situations as it becomes a 35-180mm which is either not wide (35mm end) or not close up enough (180mm end). The best option for beginner will be to get a 80-200 or 70-300 to match with the kit lens and they will cover almost all situations!