WRITTEN BY RIYA DUBEY
Vegeta is one of the strongest warriors in Dragon Ball. He is also a Saiyan like Goku. Throughout the series, it has been proven more than once that he is more than capable of unlocking Super Saiyan 3.
However, it is his conscious decision to not use it. Multiple reasons might be possible for this. Super Saiyan 3 has certain flaws that Vegeta noticed. He must have decided not to use the form to avoid falling prey to those defects.
Vegeta is much more tactical than Goku when it comes to fighting skills. He did not want to spend energy on obtaining a form that has its notable flaws.
Another reason is that Super Saiyan 2 has proven to be much more efficient and sustainable than Super Saiyan 3. Even Goku relied more upon Super Saiyan 2 than 3.
The reason that might be the most plausible one is Vegeta's rivalry with Goku. Super Saiyan and Super Saiyan 2 both were achieved by Goku first and then Vegeta.
With his Saiyan prince ego and confidence, Vegeta must have found it insulting to follow after Goku time and time again.
As a result of this Vegeta tried to not follow Super Saiyan 3 and rather focused on the Super Saiyan Blue evolved.
These are the reasons why Vegeta did not awaken Super Saiyan 3 form