Lets get some historial perspective here. X.25 and Frame are switched packet delivery services. X.25 is generally for much slowly links and is extremely useful is very bad comm areas.. 3rd world countries and such where the infrastructure is mariginal at best. It has quite a bit of overhead for error checking *native* to the protocol unlike Frame which has very little error checking and relies on the upper level protocols in the stack to take care of the error correction. X.25 is still very popular in parts of Europe ( the old East Germany), parts of Russia, South America, Middle East and others which I'm forgetting. Many times those in America forget that the rest of the world is not quite as far as along as they are.
Mike S