Depends on your use. If you are parsing a message you just received, I agree that you want to do a "has" check before accessing a field. But when constructing a message, having to manually create all the options is really annoying. (I do love the java builder pattern for protos).

But I do know the footgun of calling "get" on a Java Proto Builder without setting it, as that actually initializes the field to empty, and could call it to be emitted as such.

Such are the tradeoffs. I'd prefer null-safety to accidental field setting (or thinking a field was set, when it really wasn't).