Have you ever called a REALTOR and asked to see a house only to be told you need to get pre-approved with a lender first?  Did it make you angry, or did it make you wonder why?  Were you told you needed to come into the office before seeing the house?  Here are a few things for you to think about.

1. REALTOR safety.  You probably called a stranger.  There are enough attacks on REALTORS to make those of us who value our lives suspicious of meeting strangers at a property.  Would you want a loved one to meet a stranger alone?
2. Sellers don't like their houses to be shown to people who do not have the evidence on hand to prove they are eligible to buy if they like it.  Would you?
3. REALTORS are paid on commission rather than salary.  They don't want to drop income-producing activities to show a house to someone who is neither qualified to buy nor loyal to any one agent.  I don't want to burn my gasoline or my time only to be told thanks for coming out and showing the house, but this is not the one.
4. Sellers are contractually represented, so why don't you want to be represented as well?  Don't you want an agent working in your best interests?  REALTORS are paid from the already negotiated commission agreed to by the sellers when the property is listed 99% of the time.  You don't have to come up with out-of-pocket expenses.
5. If you call every agent who lists every property you want to see, there is no loyalty to you other than that of agent to customer.  If you have a buyer's agent, that person has a fiduciary responsibility to you by law.  They cannot tell anything about you to another agent, especially if it would potentially harm your negotiating position.  That person gets to know you and actually helps you shop for what you want or need, even to the extent that they may call you when that perfect property first comes on market.  That definitely gives you an edge over other buyers.  

There are many other things to consider when buying a house.  It is not the same as buying a vehicle.  There are steps through the process.  Select a single buyer's agent, sign a buyer representation agreement if asked, and STOP calling strangers.