Introduction:
Drona, a renowned warrior and teacher, was well-known for his skills even before meeting the Pandavas and Kauravas brothers. Despite this, he still felt the need to prove his abilities to them.

Reasons for Drona's need to prove his skills:
- Establishing credibility: Drona wanted to establish his credibility as a skilled warrior and teacher in front of the Pandavas and Kauravas. By showcasing his abilities, he aimed to gain their trust and respect.
- Showing his expertise: Drona wanted to demonstrate his expertise in warfare and combat techniques. By proving his skills, he could showcase his knowledge and experience to the young princes.
- Earning recognition: Drona may have wanted to earn recognition and praise from the Pandavas and Kauravas. By proving his worth through his actions, he could potentially secure a position of importance and influence among them.
- Competing with other warriors: Drona may have felt the need to compete with other skilled warriors and teachers who were also training the princes. By proving his skills, he could establish himself as the best choice for their training and guidance.

Conclusion:
In conclusion, despite being well-known for his abilities, Drona felt the need to prove his skills to the Pandavas and Kauravas for various reasons such as establishing credibility, showing expertise, earning recognition, and competing with other warriors. His actions were driven by a desire to secure a prominent position and influence among the young princes.