Well, the thing here is we're talking about European roads, which are descended from ancient Roman roads. You've perhaps heard the saying "all roads lead to Rome"? This is true, in a way: all roads in a given city converged on one and only one point, which was the palace of the local Roman colonial governor (Dominatrix Maximus, as the office was called). Back when nothing faster than a typical European horse (top speed: two furlongs per fortnight) was on the roads, this was fine and caused no problems.

But with the advent of the "car" (to use the typical and incorrect American term, with "autotyro" being the actual proper name) and especially of the high-performance European cars with their their ability to travel at much higher speeds -- occasionally even surpassing two or three kilometres per day -- this was obviously an unworkable system, as it resulted in frequent deadly crashes when all forty or fifty local roads reached their convergence.

Luckily, the ragtag army of Asteroid the Gallstone had purged all remaining Romans from the area, and though the palaces of the dominatrices had originally been repurposed for the use of travelling shows, they were torn down and replaced with roundabouts (due to that temporary usage, however, they continued to be referred to as "circuses", and this gave birth to the modern English phrase "traffic circle", which incorporates the memory of acrobatic acts enlivened by the need to dodge the always-incoming stream of traffic and resulting flying wreckage -- though note that in some parts of England the alternate "roundhead" was used and is the origin of the name of one of the factions in the Civil War).

Of course, this being Europe, where there is real "history" (not the mere few-hundred-years poor imitation Americans like to talk about), this process completed around the same time William the Conqueror set out on his campaign. As such, the roundabout is thoroughly ingrained into European culture, and many famous roundabouts have developed their own traditional customs and are governed by a bizarre patchwork of ancient and modern law. For example, one single roundabout in England enters and exits the City of London no fewer than thirty-seven times, and until the Omnibus Reform Act 1852 the City was entitled to impose a toll upon each entrance, with a hereditary sinecure position (Lord Garter Belt, named for both the shape of the roundabout, and the manner in which the tolls kept the City's finances from, metaphorically, dropping trou) to manage collection. Others are still subject to poaching laws which, for example, impose a penalty of loss of the right hand and a fine of four shillings for striking a deer in the roadway.

And, of course, with familiarity comes ease of use. Taxi drivers particularly are subjected to a withering battery of tests, working their way up from simple roundabouts with, say, a mere fifty-seven entrances and exits, up to more serious examples whose navigation entails potentially thousands of precisely-timed lane changes, the filing of several customs forms and two flight plans, and a stop partway through for tea. All of which eventually becomes second nature to the naturally-superior European drivers (and their naturally-superior vehicles, the manual transmissions of which include seventeen gears designated solely for use in roundabouts), and is jokingly referred to as "The Knowledge" amongst those who have passed their "O-levels".