Do you still use a wooden backing for curtain rods?

First off what type of studs are behind the wall (Wooden/Metal) as each have their own methods for being drilled into and having attachments added. Secondly make sure that you are attaching this curtain rod directly into the studs of the wall with the appropriate drywall/framing screws in relation to it being Wood/Metal. 3rd of all the reason most people use a backer board is so they can have a larger surface area to secure the item too, in most cases people struggle to find the stud or don’t know what kind of studs they have so they will attach 3/4 plywood for example to the Wall (Studs) and drywall itself, making it a bit more reassuring when not knowing exact location of the Centre of the Stud. Put it this way, if you add the rod to wall stud directly you may have 3 - 4 connection points to Per Wall, when using a backboard now you may go anywhere from 4 - 16 connections points Per wall, as you have the rod connection into the backer board, wall, studs, drywall, and other parts of the stud that the Board is now sitting on top of, as you will be connecting those to the Studs as well.