Why are there client-only encodings?

I wanted to allow WIN1250 as a server-side encoding, in light of the 
Windows port.  Now I wonder why there are client-only encodings at all.  
Without knowing details, it seems the client-only encodings are all 
"Windows world" encodings.  So was the original reason not to allow 
these as server encodings that the server doesn't run on Windows?  If 
so, should the category client-only encodings be abolished?

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/