The difference is that you might not beat Contra without some memorization, but if your reaction time and gaming intuition are good, you'll make decent progress through the game before you run out of continues even without knowing the game.

With all these bullshit SMB and SMW hacks, that's just not possible. The games are completely unforgiving and they through insanely ridiculous things at you that you can't possible anticipate. There is absolutely no chance to make it through the first few screens of the first level if you don't know exactly what you're supposed to do. And from a gamer's stand point, that's not fun. You're playing a completely linear game where each puzzle has only one solution, and that solution must be executed the exact same way every time. So I guess if you're some giant math or physics nerd, maybe the "impossible" hacks are fun, because they play to your sensibilities. Unfortunately, those sensibilities are shitty and boring, and they do not make for a fun game.