Do people still use travel agents? The only time I used one (trip was a gift) we had a bad experience. I think pretty much all the younger generation/tech savy people plan their own trips online manually.
A good travel agent makes things so much smoother. Large chains get economies of scale so you don't pay much more than online/manually, but having all the bits and bobs sorted (courtesy calls if anything changes, transfers, etc.)
Some do. (My dad does for one.) For certain types of trips a lot of things aren't online and, even if you do a lot of your own research, it can be easier to have someone else do all the email and even faxing associated with making the actual reservations.
I also sometimes use one myself in specialized circumstances such as when I'm doing a pre-arranged adventure trip of some sort and the company is familiar with logistics and other activities to add-on.