Andrew Hood, "With second at Amstel Gold, Valverde confident for remaining Ardennes races", Velo News 4/19/2015 (emphasis added):
Perhaps Alejandro Valverde (Movistar) will never win the Amstel Gold Race. It’s not for trying. And for the third time in his career, he was on the final podium Sunday, behind a superb Michal Kwiatkowski (Etixx-Quick-Step), who relegated Spain’s “Green Bullet” to second in the Dutch classic.
Francisco Almeida writes to suggest that there's an under-negation here, since the usual expression is "It's not for lack of trying".