Stupid question - if Opus 5.5 is better than Fable 5.1, why would we ever use Fable 5.1?

A user on reddit.com's dev_community posed a question regarding the use of Fable 5.1 when Opus 5.5 appears superior in almost every category. The user sought to understand the rationale behind choosing Fable 5.1 for a task, given Opus 5.5's apparent advantages. The user later expressed gratitude for the helpful answers received, indicating a better understanding of the differences between the models and their appropriate applications.

This post uniquely explores the nuanced reasons for choosing an older model like Fable 5.1 over a seemingly superior one like Opus 5.5, unlike typical comparisons that only highlight performance metrics.