Further information about the Help feature, actually referred to as Demo Mode, was released via a Nintendo Europe press release:
The feature is optional, of course, intended to make the game more accessible to players of any age or skill level. New Super Mario Bros. Wii is not going after the hardcore market (we aren’t talking about Ninja Gaiden 2). Players who will be taking advantage of Demo Mode are children and grandparents. Maybe the animosity isn’t actually about Demo Mode, maybe the current hardcore audience is just bitter that this young generation of gamers hasn’t endured the controller chucking difficulty of Battletoads and Mike Tyson’s Punch-Out!, or maybe they’re just worried these Wii gamers will, after more practice, turn out like those brats in Back to the Future II, super-gamers that can play Duck Hunt without using their hands.
Super Mario Bros. Wii launches November 15, 2009 in North America.
Sources: Game Hunters, Nintendo News, Europe