I'm from South Asia and something that intrigues me on threads about houses is that so many houses seem to have only one bathroom. Is that usually the case?
When you say 'bathrooms' do you mean rooms with a bathtub/shower in them, or do you mean toilets?
It tends to be older houses that have only one toilet. There are lots of houses in Britain that date from before it was usual to have an indoor toilet/bathroom at all, so at some point either they have been extended to add one or a bedroom has been sacrificed for that purpose.
Houses built more recently, though, tend to have multiple toilets and I've seen even quite small new-builds with an ensuite loo/shower as well as a family bathroom with bathtub.
Also, is it really considered so infra dig to live in a flat? It's absolutely the norm in cities here, so this is another thing that's puzzled me in threads.
No, I don't think so - like you say, it's fairly normal in cities.
Some types of flat have a reputation as being awful to live in but that's more to do with their construction than the notion of flats being infra dig.
In the 1960s, there were an awful lot of cheap, system-built tower blocks put up as council accommodation in the UK - often not even put together properly - so soon had problems with damp and so on, and issues with the design of estates made them ideal for muggers etc. Many tower blocks were clad in plastic to try to combat damp problems, and of course it's now been discovered that the cladding is a terrible fire risk so it has to come off.
But a modern apartment in the city, or an older well-built flat in a nice area would be regarded as a good place to live.