The javax.print API was substantially designed before merlin specs
were available. IPP compatibility is a substantial goal of the API.
IPP defines attributes which are URIs (not URLs)
Because core JDK did not include support for URI and because it
was inappropriate to define its own URI class, the API constrained
itself to using URLs.
Since then what has changed is that merlin now includes a URI class.
As javax.print is also new in merlin it would appear odd to
developers that we don't use the new class.