Manuscripts
I wouldn;t say having manuscripts returned is strictly a holdover from typewriter days. It's just as much a holdover from the first fifteen years of bad or expensive printers.
Even three or four years ago, I still wanted all my manuscripts returned because quite freqently an editor would scribble all over them, and I'd get much more useful information than I did from a rejection slip. It still sometimes works this way.
But it's becoming less and less common fro editors to have the time or the inclination to edit a manuscript they aren't going to buy, so I think it's better now to simply enclose a #10 SASE and a disposable manuscript.
I will, however, say it's still best to get the manuscript back on those occasion when an editor wants a rewrite.
Still, I've gone with the flow, and only on very rare occasions do I still enclose a full SASE for teh return of teh manuscript.