Mods, this should be moved to the CADWorx Plant forum.

You don't *have* to 2DREP a drawing. It can be printed with the viewport set to obscure hidden lines. But many clients don't want to have to deal with XREFs in their returned drawings, even if they get the models as well. Others just want dumb, 2D drawings. So the 2DREP can be put off until the return-to-client phase.

Trying to keep everything programmatically linked between an XREF'd model and a a set of 2D linework is a very, very difficult task. Most attempts I've seen are prone to disconnects, require the actual licensed software (not just object enablers), and are generally unstable even when executed under ideal circumstances.