Protobuf's answer is essentially: we defined the semantic value of a field to work like that so you don't have to consider the presence unless you have a specific need to. It Just Works™
Protobuf makes the well-trodden path the well-lit path or else people write "convenience" wrappers
![Back in these days, we didn’t have Box<T>, Vec<T>, or String. We had ~T, ~[T], and ~str. The second two are not equivalent to Box<[T]> and Box<str>, even though they may look like it, they are both growable containers like Vec<T> and String. ~ conceptually meant “owned”, though IMO that caused more confusion than it was worth.
You created a box using the ~ operator, e.g. let x = ~1;. It could be dereferenced with the * operator, and autoderef worked much like it does today.
As a “primitive” type; like all primitive types, ~T was special. The compiler knew things about it. The compiler knew how to dereference it without an explicit Deref impl. In fact, the Deref traits came into existence much after ~T did. ~T never got an explicit Deref impl, though it probably should have.
Eventually, there was a move to remove sigils from the language. The box constructor ~foo was superseded by placement box syntax, which still exists in Rust nightly2. Then, the ~T type became Box<T>. (~[T] and ~str would also be removed, though ~str took a very confusing detour with StrBuf first).](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:g6kxr7gbqzmqddvve5v6uwsg/bafkreifjgehz7kcmhqxjw3ng7hkpl4bb57yffseeq6egpg7jpjvdrxpoxu)
![From Wikipedia:
Jim Starkey coined the term "blob"[when?] working at Digital Equipment Corporation to refer to opaque data entities. The terminology was adopted for Rdb/VMS. "Blob" is often humorously explained to be an abbreviation for "binary large object". According to Starkey, this backronym arose when Terry McKiever, working in marketing at Apollo Computer felt that the term needed to be an abbreviation. McKiever began using the expansion "Basic Large Object". This was later eclipsed by the retroactive explanation of blobs as "Binary Large Objects". According to Starkey, "Blob don't stand for nothin'." Rejecting the acronym, he explained his motivation behind the coinage, saying, "A blob is the thing that ate Cincinnatti [sic], Cleveland, or whatever," referring to the 1958 science fiction film The Blob.](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:g6kxr7gbqzmqddvve5v6uwsg/bafkreicgvc6jrha7kmbnavyrqy4ge6tezyz6iwykgnv5anrphogrfh2goi)
