Why not attach XMLReader / XMLWriter to open php streams?

Hi! As documented - and several searches did not lead to a different result - XMLReader and XMLWriter can only work on an URI. That would be a php stream opened and closed by themselves. For several workflows, e.g. with php://temp, it would be nice to be able to "attach" XMLReader/XMLWriter to a pre-opened php stream. I would describe it as letting them work "on a stream" instead of "on an uri". As I didn't find anything about it: Is there a reason for not supporting 'stream resources'? Other extension, like e.g. curl, do. HPO