It's an kind of service and the people can communicate the conversation in richer manner, if the carrier supports you can share the media on call or you can send images, etc.
In India no carrier has supports the facility on default phone dailer.( Few years before jio supported but now it's not supported)
The third party app like Jio 4g voice enables this facility but it will work if the data is turned on and the same app is installed other party also.
In my point of view, the carrier was to enable the Rich Communication Service if the device supports on default phone dialer.
The device and operator want to support this facility then only it works.
