Line-oriented formats, like most traditional Unix-style tools, are for human consumption. JSON is bad at that, thus gron.
On the other hand, structured output formats, like JSON, make it easier to consume with other programs. Standard formats have readily-available and commonly used libraries, whereas line parsing tends to be one-off for every program. Whether JSON is the best format for this is certainly debatable, but it is quite ubiquitous, which is a huge advantage. I doubt many folks would propose XML as a general recommendation.
Tools should have both options on their path to maturity -- both human-consumable and computer-consumable output format options.
On the other hand, structured output formats, like JSON, make it easier to consume with other programs. Standard formats have readily-available and commonly used libraries, whereas line parsing tends to be one-off for every program. Whether JSON is the best format for this is certainly debatable, but it is quite ubiquitous, which is a huge advantage. I doubt many folks would propose XML as a general recommendation.
Tools should have both options on their path to maturity -- both human-consumable and computer-consumable output format options.