From the reading the Daylight Passenger car thread from earlier today I started to think about why manufactures/importers in O-Gauge do not sell passenger cars and E and F-units individually. Most of the passenger sets I see are just a generic 5 cars including a dome car which many railroads did not have. I am not usually into being super prototypical but it has been something that has perplexed me for years.
A lot of Passenger Trains were just a singe E or F unit a few head end cars and a few coaches. Other Passenger trains had to run through sleepers from other Railroads. I hope maybe in the future MTH/Lionel/etc can start to offer individual passenger cars to make it easier to model passenger trains in O-gauge.