York Roundtree Park

I don't know if this as been asked before but considering the search engine of this forum I can't be bothered wasting my time looking.

Considering the popularity of this site and the difficult job it is for members to get on there why is the site open to non members?

it hardly seems fair that some members fail to get a pitch knowing that there could be non members taking up the pitches.

Is the site leased for example and it's a stipulation of the lease?