Well GEICO is owned by BH, but you're right, that doesn't quite explain why BH would choose to put an ad there.

Maybe it's because GEICO is the only company/service that BH owns where every single extra pair of eyeballs that see a company's ad benefits the company. (Seeing ads on the BH page for railroad companies or electricity companies or even clothing companies probably doesn't nearly as much good for the firms as it does for a car insurance company)