I think whatever company you were working at was a few years behind the curve, because JSON was already pretty much the standard for SPAs by 2010. For example,

I think whatever company you were working at was a few years behind the curve, because JSON was already pretty much the standard for SPAs by 2010. For example, that's the year AngularJS came out, with JSON/JSONP as the only built-in serialization format for communicating with backend APIs.