I don't understand why one would let a router handle their LLM request (other than for routing it to the cheapest inference provider for open models).
When I build an application that uses LLMs, it's tuned and tested for a specific model only. LLMs are not really drop-in replacements of each other, even different versions of the same series.
The pertinent question isn't why OpenRouter but why a router company is worth 7B.