Why wasn't Hatake Sakumo (Kakashi's father) revived? Kabuto was able to revive almost all high grade shinobi figures. But I was just curious to know why Kabuto didn't revive Kakashi's father.

Kakashi's father, known as Konoha's White Fang, was a renowned, high ranking Konohagakure shinobi. Did Masashi Kishimoto intentionally avoid his ET or was there any specific reason for which Kabuto was unable to revive him?

I am asking this question mainly because Kakashi's father was mentioned in many episodes. He was responsible for killing Sasori's parents, which earned him Chiyo's hatred. He was also responsible for Konoha's mission failure for which he took a grave step of committing suicide.

ET's characters like Pakura, Chukichi, etc, got resurrected. Although they were not mentioned until the Fourth Shinobi Arc started, their ET were given more importance than Kakashi's father.
It wasn't mentioned anywhere. Kabuto never talked about Sakumo when showing off or discussing his reanimations. 

We can only assume:


They never found a body, or it was so well guarded that Kabuto couldn't get a DNA sample.
Kabuto was sure of his victory even without Sakumo's DNA, or waited for a right moment to pull him out as a trump card.
Kabuto is an idiot. (He is, what the hell did he think was going to happen when he revived Madara?!).