Back in the days when interstate highways and air travel as we know them today were still in the unimaged future, most everyone used the train for their long-distance travel.
Few people today can fully comprehend how the railroads went about meeting the demand for the various accommodations they offered including the higher-priced bedrooms. If there was a particularly high demand for bedrooms on a certain run, extra sleepers would be added. In some cases, when the demand for bedrooms was particularly high, a train such as the NYC’s Twentieth Century Limited ran in three or more sections, each section being a complete train. (Each of these sections departed within minutes of each other and arrived within minutes of each other.)
As has been discussed in other threads, the demand for Amtrak sleeping car bedrooms now exceeds the supply, despite the high prices being charged for them. (This was already the case even before the current “equipment shortage,” which has resulted in a reduction of the number of sleeping cars in service.) I once asked why Amtrak couldn’t add additional sleepers or even run a train consisting entirely of sleepers based on the demand for bedrooms. Various people gave reasons why this couldn’t be done.