So why didn't Starfleet ever give Riker a medal for his actions in BOBW?
Um, who said they didn't?
In "Chain of Command", Picard or Jellico mention how many times Riker's been decorated (did they say 5? I forget, it was several anyway). This doesn't mean dressed up in tinsel, you know. It means recognition/awards etc - one was almost undoubtedly for the Borg affair.