I'm somewhat baffled they were able to find enough people oblivious to the original Mario game to do this study.

Aside from that, I think it has something to do with how modern games are conditioning players. Games are ubiquitous now, and many elements have become common and expected when you pick up a game. When a game breaks those expectations, it throws you for a loop, but it's also part of what has made certain genres flourish (or what squashes others).

Take FPS' for example. Play one and you know the most central mechanics for them all: shoot at bad guys, don't get shot. Movement and basic controls are almost identical for FPS' across the board. WASD, shift for sprint or maybe crouch? Flashlight? Probably F. E does some sort of "activate", etc. etc.

As a consequence, people can jump from one FPS to another and hit the ground running. A developer doesn't have to worry about people being frustrated with learning the basic mechanics and giving up before they've even experienced the basics. Other game types (space sims, simulation-heavy mech games, even RTS's to a small extent) don't have this benefit as much.

It makes games more accessible when you follow a pattern, but it also makes gamers more lazy and innovation an uphill battle. If they can't see the light at the end of the tunnel, why put in the effort? I played Braid for a bit because of all the praise it got. But after about an hour, I couldn't see why I was going to like the game, so I gave up. However, I went through considerable effort to learn Dwarf Fortress because what I knew about the game made me sure I would like it.

Thus breaking the established genres is hard. Mirror's Edge did something new mechanically, but it did it by standing on the shoulders of FPS mechanics. Something like Chivalry too borrows the same controls from FPS'. People go through the effort to learn the combat because deep down who doesn't want to chop things up with swords?

Going backwards in games is much like scrapping established genres because, while there may be Marioesque platformers today, they are less common and have changed just enough from the platformers of yore to seem totally alien, and let's face it, not worth the trouble anymore.