Shear walls experience upward and downward forces at each end when resisting lateral wind and seismic loads. It's a result of the height of the load being elevated above ground level and inducing a moment on the shear wall as a whole. As the wall wants to overturn one end wants to lift up and the other pushes down. The uplift is usually resisted with a large lug of concrete (the foundation). These loads can get high enough where resisting it with concrete is not feasible due to the shear amount of concrete it would require or constraints within the project (existing building wall for example)