That's actually a great question. Banks who foreclose homes really want their money back. An innovative lender might consider in this messed up market offering leases instead of simply trying to sell the REOs they have, but tradition reigns in the financial industry. A bank is not set up to manage properties.
Their loss mitigation department would rather take a loss selling it, than leasing it out and selling it for more later. Because Federal regulations determine what operations a bank can conduct, they would have to demostrate that the property is offered for sale. A lender could find a way to place the asset into an entity that operates in real estate by managing both the sale and leasing of such assets, but only as a convenience to divest itself of the asset.
So, now that you know why banks don't just lease the properties or trade in them, you need to find a solution that works for you. In Texas a recent law now defines the responsibilites of an owner who is leasing a property to someone specifically with the intention of selling it to the tenant. The state law requires annyal reporting to the tenant-purchaser on these lease-to-own properties.
Realtors are not permitted to write up contracts that effectively create a lease-to-own situation. An attorney can draft the contract, but the landlord-seller must be willing to comply with the new state law. Most aren't interested and Reatlors are unfamiliar with such transactions.
Because the market is soft in many locations, a seller currently listing a home for sale may actually do a lease instead of a sale, in order to stop the monthly loss of mortgage, taxes, insurance and maintenance. Ask your Realtor to find you properties like that. If you can reach agreement with the seller, an attorney can draft the contract for you.
As to banks, including Wells Fargo, sorry, no lease or lease with option to buy.