Some parsers are dealing with known good input, and should not include validation code for performance reasons. Often you will parse the same JSON many times throughout a pipeline, but you only really need to validate it once. A good example of this is a scatter-gather message bus, where the router parses a message record, scatters it to a large number of peers, and gathers responses. Depending on how latency-critical this system is, it can make sense to validate and normalize the representation at the router, and send normalized (whitespace-free) JSON to the compute nodes.