In addition to services mentioned above, travel agents sometimes can also secure better seat assignments, especially if you don't have status, get fees (exchange, baggage) waived, open up seats on sold out flights, open up award seats open up lost etickets because flights weren't cancelled before flight time, or get advance purchase requirements waived.

In addition, travel agents provide services that some people either don't like to do themselves or don't have time to do. It's obviously a matter of personal preference. We all pay for some services that we could do ourselves but choose to use our financial resources to unburden ourselves of unwanted tasks. For example, doing your taxes. Unless you are quite wealthy or own a complex business, you could probably do your own taxes. But many people simply prefer to pay someone else to do it for them.