The size of JSON files is huge compared to delimited data. Languages like Python make it equally easy to consume delimited data and JSON, so it shouldn't matter much.
At work I built a system to consume feeds of numerous automotive dealer inventories and the easiest to work with is always comma delimited. There are some people out there who have no business building an XML document, and unfortunately I've had to build adapters for many of them. It takes me a few hours to get set up to consume a new CSV feed and a few days for XML, not counting mapping their industry / category / manufacturer data to ours.