Most Ridiculous Rules in RPGS

[Takewo]

Well it's like how electrical engineers always memorise Ohm's Law twice, just in case they forget the first time.

What's really weird is that once you've forgotten a spell you don't get to memorise a new one until tomorrow rolls around. So what, does my mind shrink whenever I cast a spell and then grow back while I sleep?

That sounds reasonable

Is it magic?

I've always found "because of magic" a very poor explanation. "Magic works that way because it's magic" is a circular argument. You don't need a complete rational explanation for anything that you put in your game, but I prefer that systems have some sort of coherence and consistency.

D&D 3e's explanation can be as poor as you want, but it's consistent (kinda).

"You lose a prepared spell you cast it, because you had started casting it in the morning and you are just finishing it. That's why you can prepare the same spell twice" makes sense.

"You lose a prepared spell when you cast it, because the gods so willed. You can memorise the same spell twice, though, because magic" makes no sense at all.