As long as BA loyalty is significantly less rewarding than competing loyalty programmes it would seem silly to stick with them. I don't hunt for the absolute cheapest way of getting status or how to get the most air miles, but BA has to be roughly competitive within its own alliance or vs. the viable alternatives (depending on where one flies) for it to make any sense to prefer BA over alternatives. That's probably a roughly 50% cut in requirements to even get close to AY or Flying Blue, though I've not looked into it in too much detail.