General RPGs' Rare Item Drops

Phantom Brave has been beaten for nearly a month, and now I'm working on its endgame challenges. It's kinda fun, in that repetitive level-up sort of way. Which is to say that it's not actually all that fun. But all the same, I'm a completionist, so I continue to levelwhore. At the moment, I'm trying to get an encounter where I can steal a Divine Sword, the best weapon in the game, and the chance of my running into such an encounter after a few hours of randomly-generated dungeon-crawling to get to it is about 5-10%, based on multiple strategy guides' estimations.

Why exactly DO RPG creators do this to the players? Put the BEST SUPER ULTRA HYPER PEANUT BUTTER CRUNCH ULTIMATE weapon or armor or whatever into an encounter or drop-rate of the rarest type, meaning you have to pace around looking for enemies or whatever for hours and hours and hours? Who was the clever genius who decided that players would think it "fun" to wander in a room in a moon for days to get a Pink Tail item from a 1/64 chance encounter with an enemy who drops it at a rate of 1/64? That means that at any given time while you're traipsing around FF4's Lunarian Pink Puff room, you have a 1/4096 chance that your next battle will give it to you. And that's just the Pink Tail--FF4's LITTERED with 1/64 chance items, from secret summons to excellent armor and weapons, all only moderately less annoying to get than the damn Pink Tail.

Same deal with the King Sword for Poo in Earthbound. I spent hours and hours beating the crap out of Starmen in one single area until it was dropped. I mean, it's not even like the FF4 stuff where you got new and better equipment, that you could just pass up if you wanted because it was completely possible to beat the game without it. This thing was the ONLY possible weapon you could get for Poo. If you wanted to put a weapon on him, you had to go through this rare-drop idiocy.

I don't mind having to make an effort and work for the best stuff in an RPG. You tell me that there's a ton of great items and armor in some big, over-powered-enemy-filled Cave of Trials with several immensely tough bosses in a game that's none too easy to even start with, and hell, I'll go send my cast of flat stereotypes in to get it all. You make an ultimate weapon that I have to beat the toughest boss in the game to get and therefore make it obsolete the moment I lay hands on it, and I will totally be there. Bring on the bosses, the long dungeons, and the oxymoronically idiotic logic puzzles involving pushing crates. I'll take'em all. But seriously, what is the POINT of making the ultimate reward come to you only after you've wasted a solid week walking back and forth killing the exact same enemies over and over again?