Sleepers were traditionally at the end of the train so the first class passengers would be less affected by the steam and cinders; in addition, it made possible end-of-train lounges on premier trains. This tradition continued up to Amtrak, with some exceptions, I think primarily because of tradition and the lounge position. There no longer are lounges limited to first class passengers, except for the Starlight, and lounges are generally in the middle of the train. Thus Amtrak can put sleepers on the head end and give those passengers the better ride, as well as connecting the crew sleeper to the other sleepers on Superliner trains. It does not always put sleepers on the front, but there is no longer a need for a hard and fast rule prohibiting that.