  Because hybrid machines almost never work as well as dedicated machines for a single function.  Adding "a blood component" to a mirror-world viewer would require additional components and generally complicate the design. People are versatile enough that they can change modes at the drop of a hat, but machines are stupid -- even magical machines that do things impossible in the real world. :D  We know they developed Ter'angreal that do use MW input data, so the notion that it was done and was done often, makes this idea of one too many components a dead end. They could build whatever machine they wanted. We don't know what their minimum requirement were from a data input perspective to create the experience we witness.  If the Rhuidean Aes Sedai did manufacture the Columns -- which I personally believe they did -- then how likely would it be that two master ter'angreal makers would survive the Breaking and find their way to Rhuidean to build a multi-mode ter'angreal with one mode locked out for a couple of thousand years?  I think the Rhuidean AS had just enough skill and knowledge to build a way to preserve the Aeil's history and mark the Clan Cheifs and Car'a'Carn. For them to have more than the minimum ter'angreal building skill smacks of deux ex machina.  The columns seem like a product of master makers, not a hodgepodge of spare parts and instructional manuals. 