They do have a trackpad, but not in this shape.
I was surprised when I started using the Steamdeck. The Steamdeck's trackpad felt almost identical to my trackball mouse, and it took effectively no time to get used to it.
The advantage of a trackball over a trackpad is that you can spin the ball for high movement speed, then stop it after a set time for fairly accurate distance. A trackball (or trackpad) will never be as accurate as a regular moue, but it is surprisingly usable (after a few months or practice).
