MAYBE it's because their names are hard to remember, or some casual fans can't tell one brother from the other, or maybe it's just that boxing is crying out for another (younger) Evander Holyfield.
Whatever the reason, American television viewers have switched off the Klitschkos big time, and the cry has gone out for a new, exciting, homegrown heavyweight to spark life back into the division.
Leading US network HBO has chosen to stop screening the Klitschkos' fights from Germany.
"We're out of the heavyweights, we're not playing in that sandbox any more," said HBO president Ross Greenburg. "The fights happen over there (in Europe) and they are on tape delay. There is just very little interest in the United States."
So Wladimir's defence of his WBO and IBF titles against unbeaten Russian Alexander Povetkin in Frankfurt on September 11 won't be seen in the States, unless rival network Showtime moves in and takes it.
HBO will also ignore older brother Vitali's next defence of his WBC belt in October, unless Britain's David Haye or Poland's Tomasz Adamek, who has been showcased by HBO, is in the opposite corner.
The trouble is that the Klitschkos, though technically skilled and heavy punchers, just aren't exciting enough for American fight fans, many of whom grew up in the explosive Tyson era.
No one can really blame the Klitschkos for preferring to fight in Germany, where they have large public support and can generate up to 60,000 ticket sales, as well as huge TV audiences.
Consequently, they are better paid than if they fought in the States, while enjoying what can be termed home advantage. Though born in the Ukraine, they have been based in Germany for most of their careers.
It could also be a major cause of the dwindling American interest in the Klitschkos that, however likeable and talented they are, they are foreigners.
US fans held a virtual monopoly on the world heavyweight championship for so long that they find it hard to let go. So until they find a challenger capable of breaking the Klitschko stranglehold, they're switched off.
Look at the current heavyweight ratings in The Ring magazine and you'll find just two Americans in the top 10. And both Eddie Chambers and Chris Arreola have had their chances to beat a Klitschko and failed.
The outlook doesn't look any better. There isn't an outstanding American heavyweight prospect to be seen on the horizon. Considering the history of the division, that must be hard to take.
Heavyweight has always been the glamour division, with great Americans like Muhammad Ali, Joe Louis, Rocky Marciano, Jack Dempsey and Jack Johnson on the most famous list in boxing.
Now US fans, starved of encouragement from their big men, are turning in ever increasing numbers to the lighter divisions for their thrills.
The most appetising match in boxing, if it can be made, would be between Filipino idol Manny Pacquiao and unbeaten American Floyd Mayweather Jr.
That's at light-welterweight.
Given the outstanding talent of both, the intriguing clash of styles and the immense pride at stake, it really has the potential to be a fight to remember.