In the universe of Dragon Ball Z, Goku’s transformation into Super Saiyan 3 is one of the most iconic and powerful moments in the series. However, a point that leaves many fans puzzled is why Goku does not utilize this powerful form during his fierce battle with Majin Vegeta.
The answer to this question revolves around the combination of several factors: strategy, physical condition, and emotional state.
1. Goku is not fully accustomed to the Super Saiyan 3 form

Firstly, it’s important to note that Goku was not completely familiar with the Super Saiyan 3 form. This transformation requires a significant amount of energy and intense concentration, which Goku was still learning to manage effectively.
Although he had sacrificed himself, this aspect of mastery would reduce the pressure on his physical condition, but Goku did not have full control over maintaining this powerful form. If he were to attempt to transform into Super Saiyan 3 during his fight with Majin Vegeta, he could encounter serious difficulties, especially in achieving and sustaining the transformation.
2. The time required to transform

The process of transforming into Super Saiyan 3 does not happen instantaneously; it requires time and substantial focus. As we saw when Goku transformed to confront Majin Buu, this process can be lengthy and complex.
In his battle with Vegeta, a warrior known for his impatience and eagerness to fight, it would be challenging for Vegeta to grant Goku the necessary time to complete this transformation. Vegeta is always driven by his pride and desire to defeat Goku, which could potentially lead to Goku being compromised during this critical moment.
3. Goku desires a fair fight with Vegeta

Goku is renowned for his desire to engage in fair and balanced battles with his opponents. Knowing that Vegeta is in his Super Saiyan 2 form during this fight, it is likely that Goku wishes to fight him at the same level. This represents not only a personal challenge but also a demonstration of respect towards Vegeta as an opponent.
Transforming into Super Saiyan 3 would disrupt the balance of the fight, which is something Goku would want to avoid to maintain a sense of competitive spirit and honor.
If Goku were to transform into Super Saiyan 3, it is highly probable that Vegeta would quickly find himself overwhelmed. This would not only diminish the importance and intensity of the battle but also undermine Vegeta’s pride. It could be a situation where Goku, despite his abilities, would prefer to avoid using an overwhelming advantage over his rival.
4. The energy consumption of Super Saiyan 3

Aside from all the reasons mentioned above, there is another crucial aspect to consider: Super Saiyan 3 consumes an immense amount of energy. This transformation places a considerable strain on Goku’s Ki levels, and maintaining it requires substantial stamina.
During critical moments, Goku may not have sufficient energy reserves to sustain this form for an extended period, especially when considering the other battles he may have to face in the future.