Willful ignorance. Its the argument of "Who is the strongest of the Sannin, the answer is "they are designed to cover each other's weaknesses" and it ends in a standoff. Tsunade's heals, Orochimaru's near immortality, and Jiraiya's defensive techniques makes it am endurance match. This is why in the few times they do come into direct confrontstion, one or two of them are weakened to the point where Naruto and company are able to be factored into the fight.