The answer is yes, I work with all clients by contract, and have for most of my career. I love knowing who my "Clients" are, and they love knowing that I am working diligently to locate their next home.
If I represent a Seller, there is a contract. If I represent a Buyer, there is a contract. If we are to work together, there must be a complete understanding of that relationship - and what better way to solidify that understanding than to have it in a written form.
If an Agent is unsure of of the level of committment they are willing to offer a Buyer, they would not offer such an agreement, to sell a home to a buyer.
Now, it is not an ideal situation to insist or force a buyer to sign this agreement. Better to present the agreement and if there is reluctance to sign, then an Agent should continue on to either Plan A, B or C. But before we discuss this further, either always offer or never offer this contract. You should be consistent in your business practices.
Plan A: Further discuss why the Buyer is hesitant to sign the agreement, then decide if you will let them "try you out" for a day (give them a copy, with plans to sign on Day 2); Plan B: As an Agent, decide if the Buyer "qualifies" to work with you and go forward with them signing that they reject the Offer to work exclusively with you; or Plan C: Allow the Buyer work with another Agent.
In Nevada, the Duties Owed Disclosure which is a non-committal form explaining the Agent's Duties must be presented to the Buyer.
If an Agent has not presented any of the above documents to a Buyer at the first meeting, then a Buyer should interview with other Agents until they find "the right one".