I began researching what it meant to be a writer in these modern times about two years ago. It's amazing how little we know when all we are doing is writing a book. The publishing world is under tremendous pressure to change. One thing I have noticed when researching publishers is that more and more of them are turning to giving authors no (or tiny) advances. I think this is quite logical, and I support it, however it does upset the 'way things work' regarding literary agents.
Since agents make their money from advances, there is no reason for any agent to help a writer get a deal with any of the growing number of publishers that don't do advances. Why should they when they won't make any money? A system where agents are ignoring many publishers because there are no advances is a broken system.
The ideas I have seen, such as having agents charge money to writers, are no good, as that system is too prone to swindlers and others who would take advantage of the horde of wannabe authors out there. The system works better when an agent only gets paid if their client succeeds.
I believe literary agents should evolve a new system that doesn't work off of advances, but allows them to earn a set percentage of an author's earnings. This would maintain the model of joint success between agent/writer while allowing agents to sell to any of the publishing companies.
Edit to add that Bryan (ink) says in the comments that agents DO also get 15% of royalties. In my defense, in two years of reading about agents I have never heard any of them say this. They always make it sound as if they just get 15% of advances.