Is this like Windows and MacOS not being in the top 10 of distrowatch.com?
There are so many plausible explanations for why a particular model is or is not ranked in the top 10 by this metric.
Maybe people using OpenAI models are so happy that they don't care about other models and have no need for OpenRouter. Maybe OpenAI models produce fewer tokens, or are more expensive per token.
Your conclusion might be correct, but citing the number of tokens seen by OpenRouter is not very strong evidence.
I use openrouter.ai as the benchmark because it's the foundational API layer for innovator apps that are always the quickest to adopt new tech.
But I don't think either are very meaningful when there are actual benchmarks to measure the quality of models on specific tasks.
And there's a reason that OpenRouter has an OpenAI compatible layer highlighted not deep in docs, but on their Quickstart page: https://openrouter.ai/docs/quickstart#using-the-openai-sdk
The number of projects accessing OpenAI directly, who might only reach for OpenRouter once an alternative is desired, is unknowable (since OpenAI doesn't share usage statistics), but likely meaningful.