It has to be remembered that the numbers of coaches required to run prototypical services and the numbers sold by a model shop will be totally different! I can still remember when I first started with Tri-ang TT and my mainline trains were three coaches long! They were all Composite, Restaurant, Brake 2nd. No real railway would ever have as many Restaurant cars as Composites and Brake 2nd's but I bet a lot of layouts run by under 15's do!