Well ultimately the public are the ones who fly and they make a choice as to who they pay to fly with. Hence if they ain't flying with BA the company's revenue goes down and they are less able to afford to pay large numbers of staff etc. If said members of the public find they like the alternative airline more than BA, they might not come back. The old maxim that it requires far more energy/money/effort to get back previous/new customers than it does to retain existing ones is true here.