I was thinking permanently but now that you mentioned memory and it's relation to learning attribute, I see it differently.
I have always assumed that inability to determine how many charges a wand has was related to the character's skill with magical things in general.
Then again, wands can be used and most chars will remember how many charges each still has so it's related to memory and the ability to remember learned information.
The problem here is that for example, you can still remember exactly how many castings you have on any of the 30+ spells available. Or the exact type and order of traps around mana temple. Or the amount of gold you're carrying, that can go into hundreds of thousands of gold pieces, etc.
I see big inconsistency here, where your character can apparently remember large numbers about a lot of abstract things yet can't remember something as trivial as the single digit of charges on wand(s) in inventory.