I've never used a travel agent before, and needed seen the need to. Are there any benefits aside from booking everything yourself? I know they must have some partner discounts, but surely their commission exceeds those discounts.
These days there is less need for a travel agent, but they seem to do more corporate travel for offices, whether it's trains or planes. Companies can afford it and it saves them time, though they can bill clients for it. I think they can be useful for trips that require multiple visas as they can advise and tell you the best hubs for interchange and the types of visas required, especially places like China or Russia where you can only buy a ticket once you have a visa in some cases.