Weekends All Booked Up - is it a myth?

Now the website is back to normal thought I would see what weekends are available.  Looked at a couple of sites for 2015, Chatsworth and Sandringham and they seem to have lots of space and hardly any weekends all booked (Chatsworth service pitches excepted) Rowntree seems to be full most of the time with hardly any space.  So is it a myth that all weekends are booked not allowing anyone to have a full week?

And before anyone starts I have not gone through the whole of the site network so I am sure there are other sites teh same as Rowntree that are also full but Chatsworth is one I see continually moaned about.