....because management know that winning industrial "negotiations" is a given these days when Balpa are representing the other side.
Flight crew t's and c's are easy meat that yield high cost savings with very little time wasted on brinkmanship. Tell Balpa that the airline is struggling in these hard times and they roll over in fear that their pension pot won't be topped up by subs of potentially redundant pilots.
Result = management productivity bonus + balpa final salary pension demise averted. Phew!