It would seem that kayak and all travel agency websites are at fault, then.

If I can click on a link provided by kayak that is advertising an available room, only to find when I arrive at the linked-to site that no room is available, why can't kayak have taken that little step for me and saved me the hassle?

I'd really like to think it isn't because kayak gets paid each time someone clicks on a link, even if no purchase is made at the linked-to site. Or that kayak otherwise stands to gain by being able to take credit for directing traffic to certain sites.