Amtrak trains commonly have a large crew, sometimes more crew than coaches in the train. There's the Conductor, one or more Brakemen (I think finally, after over 100 years of Westinghouse brakes, they are now called Trainmen rather than Brakemen). The latter just act as conductor's assistants and wear a similar uniform. Then there are the restaurant crew, cooks and waiters, the Lounge Attendant (barman), sleeping car porters (attendants), and on major services even coach porters. If there is a baggage car there will be a Baggage Car Man, and major services also seem to carry a Travelling Mechanical Fitter, who incidentally, with their enormous belt of screwdrivers and wrenches can be the most useful member of the whole crew on the now mostly 40-year-old stock. They (and their separate unions) all have their own perspective on what parts of the job they do. Or not. Some of these commonly travel together in the cafe car, where they take over one or more tables, but if you get the table next to them you hear everything going on realtime from their radios chattering away, plus acid comments about the railway management. Oh, I've forgotten the engineer. The traditional ethnic groupings of the various jobs still prevail to an extent.
And despite all this, it's just one door that gets opened for the coaches, and one of the Brakemen will have the job of putting down the stool at low platforms and seeing you in. Conductors seemingly don't handle foot stools, and likewise passengers don't do door handles. If you are in the sleeper you will be taken in there directly by its porter, who from the reservation list at an intermediate stop will be expecting you. In the usual American unionised way, if they don't see it as their job they don't do it, but if it is within their area, they snap to it and do it promptly and right.
Sometimes more than one door is opened just at the start point, for different destinations. Boarding at Chicago for California a porter stood on one of the stools and shouted in stereotypical pitch "Folks, those for Illinois, Iowa, Nebraska, Colorado, dis car here. Folks for Utah, Nevada, California, dem cars furrrrrrrther forward".