Referring back to the real world waxed cotton and movie leather:
I have collected reprints of UK road tests from well before WW2 untill 1980. Post war till say 1970 being 'our' vintage window, my observation is that the road testers used one piece waxed cotton coverall, two piece waxed cotton and versions of rubber/nylunn coated wool/cotton long coats and ditto baggy pants.
In the collection covering 1950 till 1960 there is ONE leather outfit when the smallest tester, Vic Willoughby, is doing top speed testing on The MIRA test track.
The period covering 1970 - 1980 sees a shift as modern nylon materials appear. Yes indeed hi-viz patches too. Noooo leather.
This is the same as my perception of my motorcycling as life style. Leather was just for racing.
Helmets much the same. Logically no full faced appearing before the end of the seventies and then only exceptionally. We by and large did not go full face for racing until the FIM made it mandatory. It has to be seen in the perspective that all but the top few racer, we were all on a budget only just enough for shoestrings. I mean the first years I róde my bike to circuits even in Belgium and Germany. Weather or no weather. Prepaired it on track. Monday morning to work on same bike.
If you dropped it, needed to hitch a ride back.
The full faced became only common on the road after the Japanese superbikes became common.
This observed, the first 'modular' helmets appeared pronto, 1980s!
Me, for road use, returned to open face when wind tunnel tested fairings became the norm. Again surprisingly early; The 1980! Moto Guzzi and ditto BMW RS are notable examples.
All in all in mý opinion our outfits are héavily influenced by external factors, by our perception of motorbike riding as much as by the practical reasons,
Me too btw. Not so much the racing image or politically correct safety crap but no doubt by ´tribal' aspects. No way was I going boy racer or born-to-be-wild-one.
Since (pre)pensioned moving to Andalucía rain proof has become a non issue so now it is all about comfort, style with mínimal protective pads if at all. Shoulder pads I woúld like in all jackets but that is because of the ti shoulder
A less applicable perspective are the tests published from 1930 - 1940. Mostly very sturdy trench coats* and not a single helmet. It must be noted that traffic was less dense, road surface often dirt and the speeds só low that in some photos the rider is smóking!
* during the sixties, early seventies in the Netherlands my father, uncles and granddad all rode their two wheeler wearing a heavy leather trench coat. Warm faux mole skin lining and buttoned straps to tie the flaps to the legs.