On tubeless wheels, punctures happen when the tire is pinched between an external object and the edge of the rim. Increasing the width of the rim profile in these points greatly reduces the likelihood of these punctures.
Asymmetric rims allow us to make a more triangular shape with the spokes from each side of the rim, balancing the spoke lengths and tensions. This means each spoke takes an equal amount of strain. In short, asymmetric rims mean fewer spoke sizes, more balanced tensions, and stronger, more reliable wheels.