Well, to answer (merely to satisfy your curiosity), you must consider
the tools that were available to the homeowner ca 1973.
Starting in the following year I began doing remodeling and additions to
our home, built cabinets and book cases, made molding and trim pieces
(yeah, still have that scary molding head). At this point I don't
honestly recall if, or of what quality, the miter saws were that were
"homeowner" grade.
I have to agree with you - at least with regard to newer RAS - about the
adjustment/alignment due to the arm. More of a problem (as I stated)
with, say, post vintage 1975 RAS that the earlier ones. I'd wager that
even today if you let me sharpen up that Freud rip blade and tweak the
adjustment on the saw, I could rip down a 14' 2x12 leaving an edge as
smooth as a baby's butt and do it ALONE or with the assistance of my
wife at the outfeed end.
40+ years ago things were different. My remodelings, additions,
cabinets and bookcases still stand and I defy you to tell me they'd have
turned out any better or worse using Fein, Festool, Jet, Powermatic, etc.
And yes, I still have all my fingers, both eyes, and no holes poked in
me by power tools. I also now have a cabinet saw, planer, jointer,
drill press, 12" compound miter saw (this is number 2), stationery belt
and disk sander and probably just about any other power hand tool one
could want.
I made do with what I had available at the time as we all did/do.
YMMV <g>