but it would make sense in that surely it would be a commercially viable route, so perhaps the only reason is that it's not physically possible?
Given that Switzerland is a mere smudge on the European map, and you've already got non-stops to SIN going from ZRH, you'd have to be doing something special to justify directs from GVA in addition to what you've already got. Supply and demand old boy.
It only takes 3 hours to drive from ZRH to GVA, so there likely won't be much interest from the freight boys either since its no doubt cheaper to road-haul across Switzerland than spend sums of money setting up a satellite site at GVA.
ZRH sees 25m passengers a year, Geneva 13 million..... by the time you discount all the short-haulers, there's probably not much left at GVA ... a statement on the GVA website supports this
"Around 95% of passengers are from or travelling to the region."