A couple of reasons that I can think of:
1. A schematic will frequently consist of several sheets - then "position on the schematic" is difficult to define, if not meaningless.
2. Many ICs have several units in a package (quad op-amp, quad logic gate, etc.) The individual units may be scattered over the schematic sheet, or may even be on different schematic sheets, for a multi-sheet circuit, so, again "position on the schematic" is meaningless for these parts.
3. The usual netlist formats have no provision to show where a component is on the schematic (or even which sheet it is on, for a multi-sheet schematic.)
The commercial CAD systems I've used (most recently Protel/Altium) also did not attempt to place parts on the PCB following the schematic layout.
Although Protel did have an auto-place function, I never used it - it was apparently only included to appease the marketing department as the placement it produced was useless (and it required some initial manual placement of key parts to give it a bit of guidance.)
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On 6/6/2012 3:00 PM, John wrote:
Is there a technical reason why pcbnew does not layout footprints with
layout that generally matches the position of components in the schematic?
--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
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