The PostScript file is being sent to the screen -- if you want to save it to a file, do something like
1dplot r.1D > r.ps
The screen output is so that it can be piped into another program for possible conversion to a different format.
However, the latest version of 1dplot now lets you save directly to a JPEG image file, which you might find most useful for inclusion (say) in a PowerPoint presentation. Also, the new graphing window has a button "save image to file" which lets you save the graph to a PostScript or JPEG file after looking at its glorious beauty.