OpenAI, frankly, benefits from the "nobody ever got fired for buying IBM" phenomenon.

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.