More than that, roundabouts are polite. Traffic signals - much favoured in the USA and Germany, among other nations of roundabout sceptics - are strict and precise and robotic. (In fact, in South Africa, that's what they are called: robots.) You stop when it's red and you go when it's green and that's that. At a roundabout, you are interacting with the other drivers around you, and to get the best out of it, you all need to act politely and courteously towards each other, by signalling your intentions, taking the correct line through the junction and so on.
Could there ever be a situation better suited to the British psyche than one that involves a set of rules and a carefully balanced system that relies on etiquette and decorum? Better yet, it's self-enforcing, allowing us all to live out our little inner desires to act as policemen and keep each other in check.
You can break the rules at traffic lights with impunity if you squeak through after the green light vanishes or if you pass a red light when there's nothing coming. At a roundabout, you have to play by the rules because if you don't you'll bang in to someone. If it's safe to go, you're not breaking the rules, and if it's not safe to go, you'd better stop. There's no way to run a roundabout like you could run a red light. (Not that you should ever run a red light either, you understand.)
Mind your manners, obey the rules and take your turn: it's not just advice for using a roundabout. It could actually be a summary of British culture.
Fame and fortune
The result of all this is that our affinity with roundabouts is well known. The French - who, according to some unpatriotic souls, have more roundabouts than we do - normally call them rond-points, but it's not unheard-of to hear them referred to in conversation as rond-points anglaises, or "English roundabouts".