Why doesn't my outlet switch switch any outlets?
Yes, most older houses were wired with half-switched outlets because they did not have switched overhead lights.
It's entirely possible that someone replaced the receptacles with new ones and did not break off the tabs between the 2 halves of the outlets, thus both top &amp; bottom outlets are always live.
Using red insulated wire to go to the switched receptacle was a convenience, but I don't believe it was ever required by code, thus there's no reason for you to be concerned about the fact that there aren't any /3 cables leaving your switches. Actually, in 1951, most (all?) wiring would have been individual wires with cloth insulation, not the modern NM cables with multiple, individually insulated wires within a sheath, so it's even less surprising that you're not seeing a red wire.
The outlets with 2 pair (white/black) of wires are somewhere in the middle of the run - power comes in on one pair, provides power to this outlet, then carries power on to the next outlet in the string.
The outlets with 1 pair (white/black) of wires are at the end of the string. Power comes in and is provided to the outlet, but doesn't need to carry on to another outlet.