I'm speculating here, but is it possible that the software used by the check in terminal was written by a company based in N. America or the software was sold predominantly for use in terminals situated in N America ?
If so, it would be natural for the software to use an algorithm that ranked N. American destinations higher than others, trying to be helpful to the likely passengers who are travelling in N. America
None of Dubai, Dubbo, Dublin or Dubrovnik are anywhere near N. America
LCY airport in purchasing the software could of course have asked the software company to change the airport ranking algorithm to better suit a London centric passenger base. This would entail much time and cost to change the software (the programmer who wrote the software probably quit for another job years ago) and go through extensive testing to ensure the software change didn't introduce any inadvertent side effects. This extra monetary cost would eventually find its way into higher charges for airlines to use the airport.
Or LCY management could decide that the existing software was good enough and the money saved could be spent elsewhere. What would you do ?