Here's why: the imperious folks who run Le Tour have decided--against the wishes of cycling's worldwide governing body--to ban the Astana Cycling Team from this summer's Tour.
Let me put this in perspective. This would be a little like the organizers of a PGA Tour event telling Tiger Woods to stay home. Or a rogue sheriff telling the Yankees they couldn't play a World Series game in St. Louis.
Astana is in hot water with the company that runs the Tour de France because last year's version of the team pulled out of the race following a doping scandal. Never mind that there's been a significant overhaul of the Astana team since then: Johan Bruyneel, who helped turn Lance Armstrong and the Discovery Channel team into a juggernaut, is now running Astana. The team has signed some of the sport's biggest names: 2007 Tour de France champ Alberto Contador and Californian Levi Leipheimer join holdover Andreas Kloden. Any of those men could win the Tour--if they got the chance to ride in it.
It gets complicated fast, but this appears to be part of a power struggle between UCI (the cycling governing body) and ASO (the French company that owns Le Tour), with the Italian company RCS (it runs the Giro d'Italia and has also banned Astana for this year) chiming in.
UCI points out, correctly, that Astana was certainly not the only team with doping riders last year. This shapes up as a battle between dopers and just plain dopes, and the Tour de France organizers are obviously the fools. Let Astana ride. Let UCI handle the drug testing.
And, for a change, think of the fans.