Why would someone purchase land designated Open Space Preserve?

[Matt L.]

I was looking at a past auction and noticed quite a few people bidding an a property designated as Open Space Park or Preserve for both existing and planned land use.  It doesn't sound like future development on this property will be permitted, so I'm wondering why someone would park their money here.  The only thing that comes to mind is the bidders own property nearby and want to ensure the property remains open space.