You would be surprised how many normal adults simply cannot reliably save a file in a known place, much less retrieve it. I'm not talking about dummies either. Try teaching some community education classes some time, it will give you a enhanced appreciation fornthose who design user interfaces for things like ATMs, pointnof sale systems and such.

Kids do do better than adults, but the are learning a particular set of interface conventions, and worse they are learning it as a language, rather than as a set of abstract principles. When the paradigm changes they often have just as much trouble as their parents.