Why do the heavyweights keep cancelling/postponing their fights?

[palmerq]

Wlad backed out of a fight vs Chisora? Did you mean Vitali because I don't recall Wlad ever signing to fight Chisora.

wladimir was going to fight chisora, I dont remember him pulling out twice though, this was before chisora fought vitalii maybe before helenius too, I cant remember .. pulled a muscle in his stomach a week or so before the fight

Wladimir Klitschko pulls out of Chisora bout with abdominal injury | Sport | The Guardian

seems it was when chisora was undefeated..