Because crew report all defects, BA management knows exactly what % of flights are experiencing customer convenience issues. Put simply, they already know it whether OP complains or not.
The IFE is clunky, old & expensive and is not the wave of the future (which is streaming content to passenger's personal devices). They have clearly made a decision to let the current iteration die a slow death and are content to toss a couple of Avios here and there when necessary.