this agent can only get money from the company after you have worked with this company more than 6 months, or more. So, ...... This is only one of reasons. Sometimes, the agent never tell you about this, may be he/she will give you other reason after he/she thinks you are not too much strong. So, I think if you are a new comer, you had better find out a job from a company directly.
On other hand, if the company doesn't has too much money, then never to find out an agent to help them........
Be careful, I said, it's usually, not absolutely.