I think the general point is 'if it works for Google, you should feel relatively safe adopting it for your own use'. It doesn't mean it'll fit every single usec

I think the general point is 'if it works for Google, you should feel relatively safe adopting it for your own use'. It doesn't mean it'll fit every single usecase. If what you need is something that is super efficient over the wire - or any other such requirement not filled by Protobuf - then maybe look for a different protocol altogether. Or design your own! But for the rest of us - the '99.999%' - the trade-offs are well understood and we'd rather go for the tool we know than reinvent the wheel or use a less maintained tool.