Naturally not that hard to write a custom JSON parser but the need itself is a bad thing.
https://github.com/zloirock/core-js#jsonparse-source-text-ac...
What you are probably thinking of is the context parameter of the reviver callback. That is relatively recent and mostly a qol improvement
The issue it solves is a big one though, since without it the JSON.parse functionality cannot parse numbers that are larger than 64bit float numbers (f.ex. bigints).
Naturally not that hard to write a custom JSON parser but the need itself is a bad thing.