The easy switching between carriers that CWS mentions was not primarily a side effect of the use of paper tickets. In those far distant days most fares, along with other things such as quality of food service, were set by IATA and on each route were independent of carrier, time of day and day of week. Flexibility began to erode with the introduction of advance purchase discounts, stay restrictions, and the growth of Revenue Management departments.

By the way, CWS, the road sign for a level crossing displays a steam locomotive, not a complete train.