Why rails is not using msgpack?

I was trying to find a way to get better performance out on our solution and I thought that there is a possibility to ge data rendered in smaller bits than json. My research lead me to this article.. https://maxondev.com/serialization-performance-comparison-c-net-formats-frameworks-xmldatacontractserializer-xmlserializer-binaryformatter-json-newtonsoft-servicestack-text/

As per this msgpack seems to be the fastest, however there is not much on its utilization on rails. I checkout the https://github.com/jingweno/msgpack_rails gem for rails to get started however not much info on making this as default for rails application.

Also there are no benchmarks available on this side of comparision for rails, it seems rails is biased on using json/yml.

Please share your inputs on utlization other data conversions at the time of serializing for better performance. BTW, Chris it would be great if you can take up this topic and shed some light. I am not sure if it would benefit all however people who are dealing with lot of data this definately may help.