You don't give us any numbers, so I am just going to give it a stab. 

Taxes.

Personally, selling my land would be a big tax bill.  Selling price - purchase price = 50% taxes.  Sell for 10,000 - 1,500 =  8,500 net.  8,500 * 50% = 4,250 taxes

10,000 - 4,250 = 5,750 net.   Now I would have to invest that 5,750 in something that would yield as good as my 10,000/acre net rent income. 

And that investment would have to be as safe as owning land. 

Plus, to me, land is stable.  Not a piece of paper.

Value 10,000 today.  Dollar crashes.  Land value 500/acre.  I believe that milk will not still be 3/gallon or what ever it is.  The value of things will be proportional.  

Just my point of view from a 73 year old retired farmer who has farmed since he was a boy.

Enjoy.  :)