Implementing a so-called "Luck Bar" would fundamentally undermine the game's economy and the prestige of rare drops. Rare items derive their value specifically from their scarcity, transforming them into a certainty would lead to market inflation and devalue the items already held by the community.
Furthermore, this sets a dangerous precedent that could eventually strip the excitement from other rare encounters like shiny or form hunting which effectively turning a thrilling game of chance into a predictable and unrewarding grind.
Solid -1