Planning ahead and making better choices are not the same thing. You could choose classes/chess moves entirely at random, and the person who gets a result of "take a level of Archmage"/"capture his queen" will still have made a better move than the person who got a result of "take a level of Commoner"/"move your queen to B4 so it can be captured."
Also, whether it's explicitly encouraged, implicitly encouraged, or completely ignored in the rules, the fact remains that someone who plans ahead in either game is better off, mechanically, than one who did not. He may be having more or less fun that way, but it is not at all true that having fun is more important than making good choices, as it's entirely possible to have more fun after having made a better choice or for your poor choice now to lead to less fun later.