Affiliated Sites - am I missing the point?

Just reading the 'deposit' thread reminded me of something that puzzled me recently.

When staying on our 1st AS we assumed we would get some sort of discount but this proved untrue - does anyone know if this is the same on all AS's?

I was surprised because the ASs' must get an awful lot of business via the club which is I assume at no cost to them.

Couldn't fault the site but had we appreciated the cost  we would've investigated other options as private sites can sometimes be cheaper.

Does anyone know why the AS's are in the club section and not the blue section of the book?

Apologies if this has been raised before and also if it's a duplicate post - my first disappeared into the ether!

Cheers