When Blender is set up to select with the right mouse button, I can click a vertex in edit mode which both selects it and allows me to drag it. This happens without me needing to release the mouse button, which is fast and I think the way any user would expect this to work. However, when I change to select with the left button in preferences, I must click and release first to select the vertex, then I can move it. Why doesn't the left click work exactly like the right click? Why does the select only happen when the left button is released? I am running Blender 2.81 on Mac OS X.