COPY not handling BLOBs

I have a bunch of data in Sybase and some of it is in image fields.  We
use bcp on this data transparently all the time without major issues in
character mode.   Is there a fundamental technical reason that BLOBs
can't be COPY'd in postgresql or is it just that nobody has ever wanted
to before?

(If I was starting from scratch I'd probably be happy with
pg_dump/pg_restore, but I'd like to migrate in easy stages over from
Sybase, so I'd like the bcp files to be interchangable.)

Right now I'm having to write a program to create all the large objects
up front and record the OIDs in a file which I will then COPY in with
the rest of my data.