The thumb loop on the wrist wrap can be used to help adjust the tension of the wrist wrap depending on the individual athlete's requirements but by no means is it crucial, most athletes will remove the loop over the thumb once the Wrist Wrap is tight.
Wrist wraps do not weaken your wrist. Wrist wraps will support the natural stability of your wrist joint in order to keep it neutral when lifting. However, your wrists won't get stronger if you continue to wear wrist wraps thinking that you don't need to implement wrist strengthening exercises.
