fair point but why wouldn't the midwife and government recommendations be stronger about requiring car seats?
Lots of things that are legal aren’t safe though, it’s two totally separate things.
A baby in a pram pushed into a black cab won’t be protected in a crash, the straps aren’t designed to secure the baby in an impact so even if you could secure the pram the baby would likeky be thrown out the straps.
In terms of people buying a seat for one use, I’m guessing most people would use occasionally, in friends/family cars, taking a taxi somewhere, want to have for an emergency incase a middle of the night hospital visit in taxi required, etc.
Or lots of people walk/bus/train from hospital if they really don’t want to buy a seat and can’t borrow one.
Obviously some people take the risk of a baby with no car seat and most will not be involved in a crash and be fine but it seems a really stupid risk to take. Imagine your newborn killed in a crash because you didn’t want to spend money on a seat or get the bus home.
Also, a hired seat is obviously safer than no seat but you would need to know how to adjust the straps for a newborn, fit it correctly, most seats have inserts for newborns these could easily be missing on a hired seat, like you say you don’t know the history of the seat. Not a risk I would take, not would I want the messing about trying to sort a taxi seat on the way out of hospital.