Why are big marathons held one right after another?
Boston, London, next Madrid. Don't the people who run competitively need more time to recover?
One is not required to attend all of them, Madam.
The most prestigious marathons are: London, NYC, Rotterdam, Chicago, and Boston. You could also add the World Championships and the Olympics, but they are very different in too many ways to compare to the others.
An elite runner will do no more than one or two marathons in a given year, depending on time of year, training schedule, other races he or she is preparing for, presumed weather conditions, type of course (hilly or flat), prize money, appearance fees, and assumptions about which other competitors will show up. It can get complicated.
A runner who might see himself or herself as one of the best marathoners in the world will not go to Madrid, UNLESS the Madrid marathon organizers decide to pony up big bucks to get a 'name' runner or two. That can and does happen. For the most part, though, the winner of the Madrid marathon would be a lot less competitive in London or Boston.
Thanks for the explanation, r2.
What r2 said, but I'd add London is the Wimbledon or Augusta of marathons. Other than the Olympics and World Championships, the top tier marathons are London, Boston, New York, Rotterdam, Berlin and Chicago (possibly in that order). London, Rotterdam, Berlin and Chicago are also reputably fast courses so world records are a possibility.
Then you have the next tier, some possibly as financially lucrative but not as prestigious: this would include Dubai, Paris, Tokyo, Dubai ... and even further below Belgrade, Prague, Athens, Rome, Madrid, LA, Honolulu, Stockholm ... then you'll have the lesser known marathons almost every wannabe city has and prices include a lifetime supply.
All these marathons are having to cap the number of Kenyans and Ethiopians who enter because they're so much better than everyone else.
Uh, it's the weather, OP.
Who runs a marathon in a snowstorm?
R5 is correct: marathons are almost always in the spring or fall, to avoid inclement weather as much as possible.