Its all about the cost & what BA are willing to pay to have newspapers loaded onboard their aircraft & lounges.
Whilst the cost of the actual newspaper will be minimal, there is a lot more to the supply chain than meets the eye...
Putting any product on an airplane is expensive. It becomes a lot more expensive (and complicated) when the product only has a effective shelf life of 18 hours, and it is produced in the early hours of each & every morning....
I am sure that even if the FT was offered free to BA in Singapore that they would still decide not to load it due to supply chain & security screening costs...