Why did Luffy not join Roger's crew in visiting Skypiea? Was it due to his age or lack of interest?

 Luffy did not join Gol D. Roger's crew in visiting Skypiea primarily because of the timing. Roger’s crew explored Skypiea long before Luffy began his journey. Roger’s final voyage, which included their trip to Skypiea, took place roughly 20 years prior to the events of *One Piece*. At that time, Luffy was just a child and had not yet set out on his own adventure. The timeline makes it clear that Luffy and Roger’s crew were not contemporaries, so Luffy was not in a position to join them.

Another key factor is Luffy’s personal journey and ambitions. By the time Luffy sets sail, he is focused on his own goal of becoming the Pirate King. His adventures are guided by his dreams and the path he has chosen for himself, rather than the legacy or past experiences of Roger's crew. Luffy's quest is to follow in the footsteps of Roger and uncover the mysteries of the Grand Line on his own terms, which means his journey through Skypiea and other locations is part of his distinct adventure.

Additionally, the exploration of Skypiea was a significant part of Roger's final voyage and had specific implications for his crew and their quest for the One Piece. For Luffy, Skypiea is one of many destinations on his own journey, and his experience there is shaped by his current goals and the challenges he faces. Luffy's time in Skypiea serves as an important chapter in his quest, but it is separate from Roger's previous exploration.

Ultimately, the reason Luffy did not join Roger's crew in Skypiea is a combination of timing and narrative focus. Luffy's adventure and the story of the Roger Pirates are distinct, with Luffy carving out his own path as he follows the trail blazed by those before him. His journey is characterized by his personal aspirations and the ongoing legacy of the Pirate King, rather than a direct continuation of Roger’s past expeditions.