All fair points above. So not every agent requires them, some do though. For context, I agree with the idea that you should not sign something until you feel confident in working with a person. That being said, it goes both ways. As an agent/broker, if the client is not committing to you, how committed are you to the client (if you ask them about this).
The quality of agents runs the gamut, but I bet you don't ask the attorney to represent you and tell them I won't pay you until I am sure you win the case (obviously some do work that way but talking about the situations where that is not the case).
That being said, if you ask someone to run around and do a bunch of "free" work eventually that tapers off as they find clients that respect their time, energy, resources (assuming they are worth their weight).
Not saying you said any of the above, but I personally sign them frequently on properties before they are presented, etc. It is just part of how people protect the fact they are doing a job that doesn't get them paid until closing...