The whole concept of two vacuum cleaners is something of a conundrum for me, because up until my mother bought an Electrolux 302 around 1978 or so to supplment her Electrolux 504 which was still very new at that time, I was not aware of people owning two vacuum cleaners. I didn't purchase my shop until 1979 and before then I didn't take much notice of what people were cleaning with.
My mother was a housekeep for numerous people over the years and was well liked by those she worked for. One family bought her an automatic washing machine; another -a Doctor- bought her the Electrolux 504. Up until that time she had been saving for a new vacuum cleaner, but when the 504 was given to her, she didn't go out and squander what she'd saved. Her old vacuum cleaner, a Hoover 262, was sent to live upstairs and when it finally died my mother -who by now was getting older and had found having a cleaner on each floor most satisfactory- used some of her savings to buy the Electrolux 302. She went for a cylinder as she really liked the advantages of both types and liked the idea of having one of each.
But when I had my shop I quickly realised that more and more people seemed to have another cleaner tucked away somewhere - in many cases people told me they inherited a vacuum cleaner when a relative died. But I know some did say they purchased two at different times.
But as Turbo500 says, it was not really the "done thing" at one time to have more than one of anything like that. Heaven knows some households didn't have a vacuum cleaner at all!