I wouldn't say Contra is about memorization save for maybe a couple parts. More about learning enemy attack patterns and training yourself to track where the bullets are going to be. Most of those NES platformers are all about learning how to deal with enemy attack patterns.
Konami code also gave you 9 lives and level selection in TMNT2.
There is a big psychological difference between having to go to a website to find a hint and just having to press a button. The latter feels like the normal course of playing the game and the former does not. That's what I mostly object to, when you don't have to make any effort to get the hint, you don't feel the same way about it.