TFC books film festivals for filmmakers when that work is too time consuming for the filmmakers themselves to handle.  Bookings can be done by yourself and you can charge fees for an in demand film. However, there is something to be said for the ability of a distributor to command more in fees and know of more fests to get the film placed more broadly.

Know your film and yourself to determine how your festival run is best handled. Especially with niche films, make sure you are working with someone who has the knowledge of all the appropriate fests and can command decent fees, or make sure that person is you. More to consider if working with an outside company: make sure they are not too glutted with so many films that cannibalize each other both attention wise and content wise and ask what they do to work the film at the festival level.