Examiners might ignore the rule because someone shouldn't be there, and it might be their fault if you hit them because they ignored the rules of the road, but personally I would rather not hit them in the first place.
To be honest I'm really surprised you haven't ever been in a situation where someone is there, because it's quite common for this to happen, maybe it depends, but there are roundabouts near me where the exits and entrances are very close together and this happens frequently.
Just as people shouldn't pull out in front of you at junctions, but they do, doesn't mean I shouldn't put my breaks on because they were at fault... Surely it is better to do all you can to avoid a situation.
Regardless of whether someone is following the rules of the road or not it is your responsibility to be safe, I don't fancy smashing in to the side of a car, it could kill someone, and whether that's 'my fault' or not, it's not a chance I'm willing to take.
I see people do stupid stuff on the roads all the time, and that's why I wouldn't just drive around airy fairy following the standard rules of the road, because other people mean that they don't actually work.