@Benjamin Summers, I think you're leaving out a key aspect of options markets and that is mechanisms necessary to cover for counterparty risk. In laymen's terms, an options market requires the ability of all parties to follow through on their obligation. At a typical options exchange (to quote Trading Places), "all accounts to be settled at the end of the day, no exceptions". This is another way of making sure all participants are credit worthy and follow through on their obligations.
You mentioned that calls are typically in most contracts. The credit worthiness of the holder of the call option isn't as important to the counterparty (the owner of the asset). If the holder of the call option cannot raise the money necessary to exercise it, then the seller continues to hold the property.
That doesn't work with put options. If you hold a put and wish to exercise it (someone needs to buy back the property at a specified price), what happens if they don't have the money to buy it back? Your put option is effectively worthless.
That's not to say these options cannot be used in the real estate world, it's just that it will require a lot more analysis on a deal by deal basis and is a long way away from becoming a commodity.