You could take that further and say that shear does not exist. It's a construct we have created to deal with tension failures in other planes. Everything basica

You could take that further and say that shear does not exist. It's a construct we have created to deal with tension failures in other planes. Everything basically comes down to a truss model. The failure you idealize as a shear stress is really a failure of a tension element in a miniature truss. This is true in bolt shear, scissors, etc. This is why the code forces you to use strut and tie model deep concrete beams. As much as you may want to idealize a shear stress, really what's happening is the beam is arching over the span.