Because Hat Club says so.
If you don’t feel like logging to facebook it’s a picture of a Yankees cap with a flag on the side. The post says all teams will have it.
If you do log on Facebook why not be a friend of the Mets Police on Facebook and like my stuff and all that so more of your friends can hear old Lee Mazzilli anecdotes.
5000x more tasteful than the annual Memorial Day & July 4th atrocities. As is usually the case with anything patriotic, less is more.