My mothers house is 1950's and also has the bathroom cold taps on the mains. Mind you, it is a bungalow, so that might make a difference.
"Many older properties have cold water storage tanks in the roof space or loft. In most cases thisstorage tank will provide cold water to upstairs bathrooms but in some properties all of the cold water taps may be fed from this tank."
"In older houses the kitchen cold tap maybe the only tap connected directly to the mains."
Every house I have lived in has been like that - 1950s, 1920s, 19th century, 16th century.
New properties tend to connect the mains feed up. I've seen two different reasons given for the usage of a water storage tank - 1) to cope during any supply issue and 2) to prevent impurities getting back into the main. No idea if either is correct.
It definitely hasn't been re-configured since my parents bought it in 1982. Again, though, there is high mains pressure there.