I will never have a Tesco's Club Card. But every single time, they ask me.
The Apostrophe cafe near New Inn Yard is much smarter. Blank loyalty cards are visible on the counter, but not offered. They don't ask you if you have one to redeem, either - you're expected to present it as you order. I've been going there most mornings for the last week; this morning, they recognised me as a frequent customer and asked me if I wanted one.
Of course I said yes. I've seen this principle at work back in the shareware days - you don't even mention registration for the first week or two - but I think more could be made of it on the web.
Ah you see you just have to get friendly with the staff and they eventually learn you'll never have one. What I found funnier is when a new person forgot to ask and I said 'no club card' - they were very over apologetic for not asking me - sounds like there's strict enforcement of the policy :(