I rememember the old rubber and plastic britches, brand new they could be leaky, especially if you had a skinny baby so the leg openings were loose! When they did work, they could work so well as to encourage nappy rash/discourage it healing, (my ex would leave our dd unchanged until I got in! Bastard). And then urine and soaps made them brittle, so the very poorest might not have seen them as worthwhil given the drawbacks. Or if they did, kept using them even once they began having little holes or the elastic at the openings started failing. (Well, i was that broke after he left). And maybe not bothered replacing them.
I remember my mom and aunt using disposble nappies in 1970 for my brother and cousin. Only for out of the house, like a family trip to the zoo, so they didnt have to carry wet nappies home. No plastic cover, just a big pad, that you had to use pins and your own nappy cover. The pins ripped the corners of the nappy of course, so they used to use masking tape to make a better spot to pin through. I am sure there must have been mothers who just used the tape!
Bonus: my grandparents moved states when my mom was a baby. I asked what they did on a multi-day train trip about nappies. They had asked everyone they knew for old towels, undershirts, bedsheets and such, and cut them up. Threw them away as they used them. On the train, that meant down the toilet, which used to just dump onto the tracks, so there's your history lesson for the day: disposable nappies 1944 style.