I can't ever imagine a need for anymore than two loos. I mean like how often will it be really that both loos will be 'in service' whilst someone else is waiting?
Quite often in this house, but we have teens who have showers that last 20mins plus 
No, but seriously, it depends where you are in life, like most things. If I were buying a new house now, then I'd have all sorts of things on my list - yes, including a downstairs toilet, yes, including at least 2 bathrooms, yes, I'd want detached, yes, I'd want parking for 3 or 4 cars - but , when I was at the stage of life when I was buying a 2 bedroomed home, then you expect the rest of the house / flat / maisonette to be 'in proportion'.... so that might mean no garden, or no garage, or no parking, and almost certainly no utility room, no second living room, and no study, and no second bathroom, or toilet.
You can transfer the same logic to what you spend on a holiday or a car or probably many other things - what you'd expect if you are paying out £500 is going to be different from what you would expect if paying out £10 000.
Most people would agree a 2nd toilet is nice, but not essential, nor expected in a small / first home.