It drags you down though. Every supermarket you go to asks for your loyalty card - which I refused to opt-in to for years, but you still are confronted with the question everytime - it gets tiresome.
I do my shopping by proxy, through a partners' loyalty card, and I've been pretty surprised at how sophisticated these systems have become.
There's a desperate battle between outlets now for custom. Loyalty cards now lead to offers (coupons) on items from the weekly shop, and our shopping basket is quite anormal I'd say. We are actually recouping some worthwhile savings, for once. Rather than being offered some promotional discount on something I have no interest in. I feel a little wrong about it, but I no longer can resist the enticement.