In reply to WaterMonkey:
From their cookie policy it is so the site can function, remember what crags you have searched for as an example.
Not all cookies are about gathering data about you, they are an incredibly useful way to make functionality work without having to store your data on a server (which is closer to harvesting data). A cookie we use a lot in work is so we can direct you down the same path on a load balanced environment so you don't constantly lose your session data as another example.
Post edited at 07:30