First, Dp2 is absolutely correct. Most agents don't know how to do them, or how they work. And many have been told that they're bad, or undesirable, and been cautioned not to do them.
There's a second equally important reason. As Deep Throat in "All the President's Men" said: Follow the money.
In a sale, the commission is earned at the time the contract is ratified, and is typically paid at closing . . . which is usually 45-60 days after the contract is signed.
But in a lease-purchase or lease-option arrangement, the actual closing won't take place for years. An agent may be willing to wait 45-60 days for a paycheck. But not as many are willing to wait 2-3 years. And even then, a lot of lease-options (and even some lease-purchases) never get consummated.
So: You're an agent. There's a house for sale for $500,000. All commissions are negotiable, but let's assume here, just hypothetically, that the commission is 6%. You sell the house (or you represent the buyer in purchasing). That's $30,000 in commissions. Depending on the agent's arrangement with his/her broker, the broker may get none, some, or perhaps half of the agent's commission. Even split 4 ways (listing agent, listing agent's broker, buyer's agent, buyer's agent's broker), that's $7,500.
With a lease-option, the most that an agent may immediately see is his/her split off the rental agreement. Assume hypothetically (because it's all negotiable) that the house rents for $2,000 and that the commission is one month's rent. That's $2,000 in commissions split 4 ways--$500 to an individual agent.
Hmmm. Which would you rather have? $7,500 or $500?
Follow the money.
Now, IF the house sells 3 years from now and IF the agent is still with the same broker (because it's really the broker who gets the money, not the agent), then, yes, the agent gets the commission for the sale. That's a lot of "ifs" and a long time to wait.
Wendy Patton, a Realtor in Michigan who is something of a lease-option "guru," has come up with a partial solution. Some of the option fee that the tenant-buyer pays the owner can, in turn, be advanced as a portion of the commission. That substantially "sweetens the deal" for the agents involved. But it's still not equivalent to making the sale today.
So: Two pieces of advice.
First, as Dp2 suggests, contact some investors in your area. Some will have prepackaged lease-options for you. Yes, they'll make money on the deal, but it'll still work out well for you. You can find investors at investment clubs. Here's a link to the ones in Pennsylvania: http://www.creonline.com/real-estate-clubs/pa.html
Second, if you want to search for lease-options on your own or with a Realtor, here's a blog I wrote on how to do it: http://bit.ly/findaleaseoption
Hope that helps.