Why? Maybe because BA tends to bend the rules more for Gold renewal than for Silver?

Amongst my own friends (which I admit may not be representative) Golds are usually obtained at least partly with business travel. I can think of a few examples of friends, both employed and self-employed, whose business travel has greatly reduced and have lost their Golds cards.

My Silver friends, on the other hand, tend to have little difficulty making Silver with personal travel. Even if they didn't originally get the card that way, they'll certainly make sure to do enough personal travel to keep it. In fact many are finding it easier than ever. Not only are sales greatly reducing typical club fares, but I know a lot of people whose personal travel has massively increased as they make the most of periods of redundancy. Of course this latter point wouldn't generally apply to people with children.

I'm not saying you figures are wrong. But I don't quite follow your reasoning.