So, we’ve all heard about how monstrous Akainu is, that Oda said the story would end in a year if he was a pirate. That means he would be able to find the One Piece in a fairly short time.
Now, as leader of the Marines, the most powerful force in the World, he could get to it even faster with them, and they’ve proven willing to commit insane amounts of strength to one task. To me, this means one of two things: The World Government doesn’t want what’s at Raftel or they are terrified of it.
With their knowledge, they’d likely know if a great weapon or treasure disappeared from the seas before Roger died, so if it’s this one, I doubt one of the great weapons is there. The other option is the one I like more. Whatever is there, is too horrific to ever emerge. I can see the Gorosei ordering Akainu not to go after it, because they don’t trust even him with the secrets and weapons stored there. Now, we probably won’t know anything about it for another decade, given how long this story is, but that’s what I like to think. The pirates are bad, the Yonko are terrible, but the truth is a nightmare, something so bad that even the most fiercely loyal marine, willing to murder anyone who questions authority, isn’t considered worthy of the knowledge. And the guy who said he’s willing to destroy a country to get meat is gonna get it.