Because what you're asking it to do is nonsense. A List<ThatHappensToContainAFoo> is not the same object as a Foo, but you're expecting the JSON parser to read your mind and do the conversion.

JSON is the leading data interchange format for web applications and more. Here’s what you need to know about JavaScript Object Notation.

Learn about JavaScript Object Notation and JSON objects and arrays, including how and why they're used. Also, find out how JSON compares to HTML and XML.

With SQL Server 2016, you can store JSON objects in your rows. Here’s how to work with JSON objects, including how to update them once you’ve found them.

JSON-LD extends JSON to include linking information. Here's how it could make JSON a top-tier player in hypermedia and the semantic web.

JSON-LD enables organizations to readily access data stored in document formats and a variety of semi-structured and unstructured data as well.