User blog comment:Fliu/One Piece Fan Short: Bartolomeo meets Shanks/@comment-24850639-20170822171724/@comment-53539-20170822201342

Only a fraction of those pirates make it to the New world, there are likely hundreds of crews we haven't seen. Most of the pirates that were around in our own worlds piracy age weren't famous and only a % are known thanks to more or less one source.

My guess on the Straw Hat situation is this; he didn't put it on his flag, he choose to put the scars on there instead. The symbol on the flags is meant to represent something, Luffy's hat is representative of his reason for being at sea. Lets presume the same thing for Shanks; so in the end, his current reason for being at sea is those scars. Shanks would have been known a little a rookie on board Roger's crew, but we don't know when he became a Yonkou. He was a famous pirate by the time he got to the new world, but he was one of hundreds of pirate crews doing the same thing. By the time he became a Yonkou, would he already have visited Luffy and lost the hat? Maybe, in that case the MAJORITY of Pirates around wouldn't know him by the hat.

It was stated when he met WB that there are not many pirates left from Roger's day, meaning that at this point the majority of people who would know about him and the hat are gone. And being a rookie on board Roger's crew particularly, he wouldn't have had many from that era even paying attention to him. Whitebeard only knew him and Buggy because they fought with Roger a lot and faces became familiar on both crews sides, I imagine due to Shanks' red hair and Buggy's red nose likely made them more easily memorable especially since they were always together.

In short... Its quite easy to understand that few would even know about Shanks once having the hat. In fact... We know Roger had it before him, yet how many even acknowledge that? Even less then those who acknowledge Shanks having it. :-?

Edit: also don't forget burning a flag in OP means "I declare war on you"... So... erm... Good job breaking it Bart!