The idea came into being in (West) Germany in the late 1980s, after the Deutsche Bundesbahn had abandoned the use of steam engines in 1977, and effectively had them banned from their rails with the de:Dampflokverbot, applied also for Sonderzug chartered trains.
The intention was to portray DB as a modern, fast and clean enterprise aiming for electrification, rather than the slow and dirty choo-choo-train of old.
In the German Democratic Republic (East Germany), which had to rely more on coal and lignite, steam was phased out by Deutsche Reichsbahn in 1988, shortly before unification in 1990.
The background was that there were still many operable steam locomotives on the territory of the former GDR, the infrastructure (e.g. sheds, water cranes, coal handling systems, sanding systems) was still in place on many lines, and the usually low maximum speed permitted the use of steam locomotives.
In southern Germany, the Bavarian Railway Museum (BEM) established itself as a scheduled steam operator from 2016.