Oh goodie ... it must be springtime in the northern hemisphere ... a waving thread!
Why don't
you lighten up? Is your cycling self esteem so poor that you
need cyclists to wave to you?
Let other cyclists ride the way they want to ride. Could be the cyclists who aren't waving are actually paying attention to their surroundings ... dodging potholes, listening to traffic, etc. Could be the cyclists who aren't waving are in the middle of a training routine and are focussing on what they are trying to accomplish. Could be the cyclists who aren't waving are tackling a challenging bit of the route and need to concentrate. Nothing wrong with any of that.
We're all different, and ride for different reasons, and ride in different ways ... sometimes all in one ride ... welcome to the world of cycling.