Mixture
That makes some huge assumptions! There are many other people who travel in business class than BA card holders.
Lots of reasonably well off folk going on holiday, joining cruise ship, visiting relatives, going to second homes etc. etc. etc.
You also don't just become Silver or Gold card holder you build up to it so don't get those advantages. As you probably well know you can lose your status as well.
So I reiterate my points that Club Europe is more than a seat and a better meal
