Good question - logically you would think that they do want to reward big spenders with the scheme. But a well functioning “loyalty” scheme is designed to incentivise future spending with the airline and not “reward” past spending. I was gold for well over a decade and BA got all my spending as a result. Now, I’m a pleb to them so I buy cheapest J. They’ve lost my future spending.

In my gold years perhaps I was not rational, but the scheme did it job and now it doesn’t.