I used to wave a lot but not as much now that I have a bell.
It's a great all-purpose communication device.
Depending on the circumstances, it can mean
.. Hi Neighbor/Friend/Familiar/Police/City crew worker/farm animal/
.. Passing on your left
.. Hey riding bikes is fun [the 8 year old on his first bike ride/experienced cyclist riding in miserable weather]
.. Get out of my way! Pay attention!
.. Don't pull that **** again