Hidden Skill Value in Games

Many video games work with lots of numbers, as such with most computer programs. Usually in video games, you are presented with the important numerical values, like your health (HP), how much money you have, scores, and more. But there are also games where there is a hidden value that the game keeps track of that they don't show to you, and often times, this is your "Skill Value", or your proficiency at playing the game. Is there a reason for these "Skill Values" to be hidden from the players, or is it hidden because of its insignificance to the gameplay?

I bring this up because I recently picked up 3D Classics: Kid Icarus from Club Nintendo for 150 Coins. The game being a 3DS port from the old NES Kid Icarus game, I didn't think much of it when jumping into the game. However, after completing my first run, I realized that the game has few different endings, depending on several factors. Among those factors is to have Pit's attack power maximized when defeating Medusa, and in order to achieve that, you must get all the power upgrades from the rooms. This is where the Skill Value comes in though, as if your skill value isn't high enough when you enter these rooms, you simply won't get that power upgrade. More specifically, here is a quote from a GameFAQs guide by Ultimortal.

A huge thanks to Disch Wersher for studying the ROM and finding that what
actually determines if you get a Strength upgrade or not, is a hidden stat
which keeps track of your "Skill", as Disch calls it. In short, how many
enemies you destroy, how many hearts you collect, how much damage you take and
how many arrows you fire, all in the same Section as the Strength upgrade
chamber - whenever you finish a Section (where you can see your XP being
tallied) your Skill is reset to zero.

To get a Strength upgrade in a given Section, you must have at least 10000
Skill. Fortunately you cannot have a negative value. These things affect your
Skill:

 -300 for taking damage, except for damage tiles like lava
  -10 for firing an arrow
 -500 for breaking a jar in the Treasure chamber
 +300 for entering a Holy chamber
 +100 for defeating an enemy that drops a small heart
 +300 for defeating an enemy that drops a half heart
 +500 for defeating an enemy that drops a big heart
 +100 for collecting a small heart (if you have less than 998)
 +300 for collecting a half heart (if you have less than 994)
 +500 for collecting a big heart (if you have less than 989)
 +100 for collecting a mallet
+1000 for collecting or buying back a Weapon
 +100 for buying anything in a shop except a Glass or Weapon
 +300 for entering the Score tally screen (redundant)
+8000 for killing a boss (redundant)

Note that some enemies are special - if they don't give you any XP, they don't
give you any Skill either. Damaging Medusa also doesn't affect your Skill,
eventhough it gives you XP.

Seeing this list here, a lot of the things you do count towards (or against) your skill value, and is actively important for getting the power upgrades. So does it make sense to have this value be hidden, or be included somewhere?

As a player who's aiming to get the upgrades, naturally, you'd want to see it. On the other hand, players who don't know anything about the skill values, and what determines getting the upgrades or not will play however they see fit. Once you've acknowledged it however, players can start obsessing over it, by not shooting any unnecessary arrows, or feel forced to spend your hearts at shops when you come across them, even if they're saving up for something better later on. This sort of behavior change is probably not what the game designers want, which is surely why the value is left hidden. In fact, when you see someone else get a different ending, that may encourage players to play it again to try to figure out how and why things went differently each play through. Certainly, hiding the value from players is a good idea in this case.

But another question is, whether if all the things that changes the skill values are appropriate or redundant as it is listed. For instance, why not take away skill values if you take damage from damage tiles like lava? To me, it seems like an even greater mess up than getting hit by an enemy if you were to fall into a pool of lava. Should you really get +1000 for buying back a weapon that got stolen from you in the first place? Could that not possibly encourage someone to get a weapon stolen to buy back later for points? Not to mention the amount of time spent on the level isn't considered either, not that it makes too much sense for getting points for the finishing time when the value matters before the level ends.

Another instance of a game with a hidden skill value may be the recent Mario Kart games. Or more specifically, hidden requirements for each star ranking for Grand Prix mode. A lot of players wants to know how to consistently get 3 star rankings in Grand Prix mode, and under general understanding, 1 star is gained for placing first in all four races. Another star is gained for staying in first place for more than 50% of the time past the first lap of each race. As for the last star, it doesn't seem that anyone is certain about how to get it. Surely the developers used some sort of formula for these rankings, but this formula has eluded many players for a very long time, leaving only theories.

As for the benefits of having a 3 star ranking is relatively small; just having 3 stars next to your name when racing, particularly for online play. But does it make sense for these star rankings to remain a mystery as to how to obtain them? For the most part, they'll just happen as you play the game and get better at racing, but what does hiding this method add? I suppose replay value for those who really want those 3 stars, but is replay value alone a good reason to do so?

I'm trying to think of other games that uses similar hidden values that is used to determine things, but I'm drawing a blank. How do you feel about games that hides these values from you that may seem important? Feel free to leave a comment below with your thoughts and any other games that uses these similar mechanics.