Player were asking for more challenging not better rewards. Or was challenge a reason to tie to rewards?
In theory no one will play a mode with any kind of challenge if there is no extremely great reward at the end of it?
Hard mode is just the same as camping in a mission for a few extra waves or minutes. It's the same exact mission. No one expected better rewards camping in a mission, or did they?
edit: If so, I believe the mode should be called something else, possibly Reward Mo