barryt Would you rather BA was a bit behind in getting a fancy new a/c - or a long way behind by introducing a machine that takes time, care, attention and money to get right? However smooth the introduction is, the time, effort and £££ for a carrier to be the launch customer is truly massive. There will be delays and cancellations that affect the whole of the fleet and many, many pax. In the long run - that can be highly damaging.
Small and new companies need the publicity of being launch customer and will take the 'hit' of the downside to be the test bed for the manufacturer. OTOH big companies do not want that and will avoid the risk. As I recall, VS stated after being launch for the A340-600, Never Again.