That's a keen observation @Jerry Freeman :
You know, in the past, I went and looked for as many JFK motorcades as I could find... there are many, so maybe some would say the crowd waves... I know from the JFK library, there is the photo from Nashville. Are they waving? It looks like they are mainly clapping.
Click on image to enlarge.
And as I have said earlier, there are a number of photos one can look at of other motorcades, LA, San Francisco, Milwaukee and so on.
When I see that picture of JFK in Nashville, the father of Al Gore, then governor of the state is in the car too, I can't get over how wide out in the open JFK is. While, at youtube, if you hunt down his appearance in LA, the security is really high, SS flanking the car as it trolls along at a very low speed.
The above image seems to show "clapping" is more common than "waving".
The guys in suits and shades to me, look like Secret Service. They could all be bystanders for all I know.