Naruto activate Kyubi power when he is in emotional distress like anger.
But Naruto is also the type that goes Kyubi mode if someone dying infront of his face.
For example :
1. When sasuke tank haku attack and "die" naruto goes rampage.
2. When he found garra dead, he goes to third tail.
3. When orochimaru taunt naruto about sasuke.
4. When Hinata get stab.
The reason why he doesn't go Kyubi when jiraiya and kakashi dead is he doesn't see their dead.
Then why he goes fourth tail when sasuke get mention by orochimaru? That because sasuke is his love friend who will die when orochimaru take over his body. Like when sakura almost dead situation in naruto vs garra.
Oh and naruto beat garra with the power of love... Oh I mean power of rival.
Yeah, I'm sure there is a huge difference between simply hearing about someone being dead/killed and actually seeing someone get killed in front of you with your own eyes. The emotional response is more than likely far stronger for the latter than the former.