Well, I can say that my kingsnakes and cornsnakes like to climb around if they get the opportunity (the kingsnake to a greater degree, however.) Of course if you add climbing furniture be sure it's setup so as to prevent any major catastrophe in the event the snake(s) should dislodge it... If you buy your branch where they have tanks you can try it on for size, or you can glue or screw hooks or suction cups to the furniture as well for added security.
Is it required? Not exactly. Will your snakes be happier and healthier if they have things to climb? Irrefutably, if done in a safe manner.
^Curtis