It's not broken. It just never got implemented. It's not an easy file copy. Audio CDs need to be extracted/ripped ... Currently I'm using Foobar2000 or ImgBurn for this job. But I agree, would be nice to have it directly in Reaper ...
This is something that REAPER really should have built in. Justin has said previously that it is something relatively easy to add and would add this if enough wanted it (if memory serves me right).