Comment by wg0
Protos don't work out of the box in any browsers as far as I checked last time unless you're willing to deploy a proxy in front to do the translation and it requires extra dependency on the browser as well.
Plus - tooling.
JSON might not be simpler or strict but it gets the job done.
If JSON's size or performance is causing you to go out of business, you surely have bigger problems than JSON.
Right, I find the use of protobuf lacking with direct support in the browser. Since JSON is a native data encoding format of the browser (effectively), it's just easier to have a JSON-based API.
Yes, there are abstractions or other hacks that would bolt on protobuf support in the browser, but that's not ideal in my mind.
Protobuf is an ideal exchange format when you're not dealing with the public as a whole. That is, a private or corporate API for your data processing pipelines, etc.