Hard modes are some of the most popular encounters in Wrath of the Lich King. They grant better loot and extra rewards like mounts and rare titles, especially for specific server firsts. However, I'm of the opinion that ever since Ulduar, we've kind of lost sight of how the hard mode encounters should work and have instead just started making everything have a hard mode.
Frankly, the Gunship encounter in ICC, while fun, shouldn't have a hard mode. It's not really even hard; it's just free iLevel 277 gear for turning on a toggle. I blame Trial of the Crusader -- and specifically, having an entire separate raid lockout for Trial of the Grand Crusader -- for this. I realize I may be on the losing side of this divide, but I really don't think every single fight needs a hard mode. Some fights, sure. The four wing bosses of ICC, absolutely. The Lich King? Heck, it could be argued that Arthas should have taken a page from Algalon's book and only had a hard mode, or maybe Sindragosa should have been a hard-mode-only fight instead of a wing boss, and you only get to fight her after the Lich King is dead in some sort of doomsday scenario where she's chained up by Arthas and breaks free to destroy Azeroth in case of his demise.