Surfaces covered with end-anchored polymers under good solvent conditions have excellent tribological properties. Friction between such surfaces is commonly attributed to the interdigitation of opposing polymer brushes. However, this conclusion tends to be based on idealized geometries neglecting capillaries or surface roughness. Using molecular dynamics simulations, we find that, depending on the direction of motion, dissipation due to capillary and shape hysteresis can contribute in a similar fashion as interdigitation. The two alternative mechanisms are even likely to become dominant at small sliding velocity. We also analyze how friction can be tuned through the solvent quality, thereby providing guidelines for the optimization of the investigated systems.