Why Did Roger Keep the One Piece Clues a Secret?

The monologue in Big Mom when she was defeated by Trafalgar Law and Eustass Kid in yesterday's latest chapter in the One Piece manga series really brings something new to the story. 

Initially, Big Mom was so confident in her position and strength as a Yonko that no one could beat her.

However, in chapter 1040 yesterday Big Mom finally had to admit defeat. 

He was finally defeated by two new generation pirates. 

Big Mom then seemed to be looking for a scapegoat for her defeat, and Big Mom blamed Gol D. Roger for everything that happened. 

Big Mom blamed why Roger had to tell about the existence of One Piece, which provoked many new pirates.

However, that doesn't seem to be the case. 

Big Mom is not looking for a scapegoat for her defeat by blaming Roger, but rather hoping that Roger will provide clues about the whereabouts of One Piece. 

This is the opposite of Luffy.

Luffy just doesn't want to listen to any clues about One Piece's whereabouts. 

And that's probably also the reason why Roger didn't give any clues regarding One Piece when he was executed. 

Roger doesn't want anyone looking for One Piece to know what One Piece really is

Roger wants someone who is very strong and very brave to be able to adventure to the end or the end of the world (Laugh Tale) like he did before. 

Roger wants someone who is willing to venture with all his strength and determination to Laugh Tale and is willing to accept for the worst that One Piece is not what they imagined.

One Piece may be something very priceless, but not gold or other treasures. 

Rather it is a treasure trove of lost historical information about the lost century, which he wants to reveal to the whole world. 

That way, the world can know what really happened at that time.

To get to Laugh Tale, one needs the ability to be able to read Poneglyphs. 

So Roger deliberately didn't tell him where it was, because someone who was able to find the location of Laugh Tale meant that the figure could read Poneglyphs. 

And by being able to read the Poneglyphs they will be able to find out what the secrets of the unknown world are.

In addition, by not telling what One Piece is and where it is located Roger knows that whoever finds it will do something about the contents of the One Piece. 

Roger can indeed reveal what is in One Piece, but is there any guarantee that the whole world will move to stop or destroy the sky dragons or the World Government?

There is still much needed for this. For example, it still takes the existence of three ancient weapons to destroy the World Government or stop them in their tracks. 

And because when Roger was executed Poseidon wasn't born yet, so he couldn't do much and Roger didn't have much time to instruct the next generation.

That's why he used his last words to trigger the younger generation to become pirates, in order to give rise to a new young pirate who could continue what he couldn't do. 

By starting the Grand Age of Piracy or the great era of pirates, Roger hopes that there is one person who can become the figure he has been hoping for.