I doubt that would fix the issue. The real cause is that programmers mostly deal in fixed-size integers, and that’s how they think of integer values, since those are the concepts their languages provide. If you’re going to write a JSON library for your favourite programming language, you’re going to reach for whatever ints are the default, regardless of what the specs or type hints suggest.

Haskell’s Aeson library is one of the few exceptions I’ve seen, since it only parses numbers to ‘Scientific’s (essentially a kind of bigint for rationals.) This makes the API very safe, but also incredibly annoying to use if you want to just munge some integers, since you’re forced to handle the error case of the unbounded values not fitting in your fixed-size integer values.

Most programmers likely simply either don’t consider that case, or don’t want to have to deal with it, so bad JSON libraries are the default.