Comment by cogman10

The benchmarks between the two are close and the engineers that have used both (like myself) can attest that the differences aren't so wide as you might believe.

I'd say that yes, ignorance plays a role here because a decent number of engineers are looking strictly at the benchmarks and choosing Opus just for that reason.

But I'd also say that a major factor for Opus use is because Opus is being purchased for the engineers by their employers. They don't get to pick which models they are using.