This has not been my experience. Generally I do pin to 1 provider, or 1 provider with a couple fallbacks (especially with deepseek - most providers are 10x the cached token price compared to deepseek themselves), but even when I don't I still usually see 99%+ cache hit percentage. Specifically using pi with various ad-hoc customisations (that I was careful not to break prompt caching with).
Because they don’t want to sign up for 10 different providers and subscriptions/etc, especially if some models are just going to receive light, or rare usage?
