Diki,
Module version or rack versions in arranger format may not be in as high demand, but they sure as hell are in high demand with the top workstations. The Korg Triton Rack, and Yamaha EX5-R sold well. Hell I can't tell you the number of personal and large scale studios that I've seen that had both the Triton Rack, and Yamaha EX5-R in the same rack shelf, one on top of the other.

So maybe module demand might be a fraction of the arranger line, but module demand would not make up a small fraction on the synth end. Full modules/racks "do" take away from the sales of the keyboard itself. If they started making these things again sales of the keyboards would without question drop.