Two solid reasons: defensive and offensive ACM/BFM remain relevant
I'll address the defensive issue first. Even if a pilot will never get into a dogfight, the pilot / aircraft still must defeat or evade a surface-to-air or air-to- air missile. This combines the use of both countermeasures and 3-dimensional maneuvering to cause the guidance system inside the missile to lose it's lock on the aircraft. To get the turn rate and axis-change-rate needed to deal with modern missiles requires the ability to pull a significant number of g's. You can look at is as a "purely defensive dogfight" technique. You fight the way you train, so you need to train for this likely situation.
The offensive high energy, high-g capability has to be retained because in real life, the rules of engagement do not always allow for a BVR (Beyond Visual Range) engagement. Further that point, even with BVR engagements allowed, if the opponent has good defensive technique versus your missiles you may still get into a dogfight-style of engagement in order to defeat or destroy that opponent. You have to know how to do that, and train for how to do that. It is an acquired skill. (The basics of the skill were eloquently laid out by
John Boyd, which is where the OODA loop model comes from).
Both the offensive and defensive applications of these maneuvers require skill with and acclimatization with high-g maneuvering.