"Not very dependent" is subjective. The objective relevant take is it is a required dependency of parts of officially supported APIs of major GCP services that have large paid customers with SLAs. It can't go away anytime soon.

Google may have Stubby as the primary internal RPC, but several other large companies rely primarily on gRPC and have contribute to it and have incentives to keep it alive, e.g. Dropbox, Netflix, even parts of Apple and Microsoft. In fact, Microsoft's support of gRPC in C#/.NET is arguably more first-class and polished than any other language.