According to this ad in the Retronaut, in 1915 over 70% of homes had no bathrooms; You could make a fortune selling these Robinson folding bathtubs. The ad claims:
I wonder, given how few baths people have today compared to showers, why there isn't something like this on the market today, a folding bath that you bring out for those special occasions, just a shower for the rest of the time.
An absolutely new invention that has taken the entire country by storm. Nothing else like it. Gives every home a modern up to date bathroom in any part of the house. No plumbing, no waterworks needed. Folds in small roll, handy as an umbrella. Self-emptying and positively unleakable.