Why is the McRib only offered occasionally and why so randomly?

The McDonald's McRib, a sandwich that has 70 ingredients but no rib meat, was first introduced in 1981 and wasn't much of a hit. But in the years since, it has established a cult following, and when it returns to the menu sporadically, those fans come out of the woodwork. That scheme is both accidental and deliberate, and understanding it requires a lesson in McDonald's business model, supply-chain logistics, and marketing.

This brings us to the McRib- a confluence of several people's work and an accident of history. To wit, it exists because McDonald's underestimated the demand for Chicken McNuggets and needed an additional item to offer to balance things out a bit.

The goal of a restaurant like McDonald's, when adding a menu item, is either to bring in new customers that would not have eaten at a McDonald's or to get existing customers to choose a higher margin item than they would have otherwise ordered. To do this, McDonald's will test and then roll out new foods.

When a menu item is successful, like the Big Mac or Chicken McNuggets, McDonald's needs a steady stream of ingredients to support the demand. It must also be at a price that leaves them a large enough margin to justify the work involved.

Enter the Chicken McNugget, which was a hit, but they couldn't source enough chicken to meet demand. To the extent that new patrons were lost because they were turned away when they didn't want a burger, McDonald's was facing an opportunity cost. It needed to find an alternative dish that this new group liked or loved as well. To solve this, they turned to their new Executive Chef Rene' Arend.

That explains how McRib got its start, but the story of its continuing return and disappearance is explained at Today I Found Out. Hint: it's not random; it just appears that way to customers.