Deterioration of service costs them nothing unfortunately. They can "enhance" left, right and center, double the price of flights and yet people will happily pay more and more for this. Yes, there is a decent enough network and connections may be good at times, but a lot of people will never change their habits / routine; wouldn't be seen dead on other (potentially low cost) airlines; be delusional and keep wearing their rose tinted glasses.
Look at all these Sofia flights. Full of people doing their last minute runs to keep their gold cards that they might utilise a couple of times a year. The BAEC keeps people flying with BA / OW, and it offers benefits you can't easily get elsewhere.

At the end of the day, regardless of what you spend and/or status, unless you're someone who has real commercial benefit to them at that given time, you're no-body, and if you stop flying, there will be someone else to take your place and so on.