O valor padrão está na coluna 'definição', tente executar a consulta sem onde:
SELECT c.name ,
col.name,
c.definition
FROM Rem.sys.default_constraints c
INNER JOIN Rem.sys.columns col ON col.default_object_id = c.object_id
INNER JOIN Rem.sys.objects o ON o.object_id = c.parent_object_id
INNER JOIN Rem.sys.schemas s ON s.schema_id = o.schema_id
