I grew up in a house with an indoor loo and my parents STILL use a twin tub.
The first house I bought had an outdoor dunny (which I had moved indoors) and then I bought a house with no hot water service or pump so until I got the plumber/electrician in I got to boil the kettle to make warm water to wash with in a bucket, and it was winter so the water I was getting from outside via bucket was invariably frozen.
However, that was only for 2 weeks not my entire childhood
My third house also had running water issues (cold water was plumbed to a header tank with holes in it) but it had solar hot water at least, and an indoor toilet as well as the outdoor one. Very high tech.
We only have a single tub in our bathroom. However I stayed at a posh hotel once that had a twin tub. Massage jets and everything, it was very romantic.