Back when I was driving a British sports car, it was the rule, rather than the exception, to wave at other British car drivers. It was a cult of sorts, a bond formed by not only the enjoyment we got from our cars, but an acknowledgement of the constant attention they demanded. We were comrades in arms.
As cars have become more reliable, they have at the same time become appliances, like a toaster oven. You plug it in and it works, period. No muss, no fuss, and no tinkering required. Less driver involvement required to keep them running. They are less personal than cars used to be.
Enter the Sprinter. As was pointed out, so many of them are driven by so many sorts of people for so many purposes. Employees, tradesmen, family people who look at it simply as a station wagon, and RVers who use them for camping. Many of these folks NEVER owned a vehicle that created a sense of comradeship any more than owning a certain brand of toaster oven does. They don't "get" the wave. Most are trying to get to a job on time, trying to deliver their kids to soccer practice after piano lessons, on their way to a favorite camping spot, and are not even looking out of the windscreen with an eye to what's coming at them.
Bottom line, I suspect waving is a very unrewarding experience in a Sprinter, and anyone doing it will probably burn out in rather short order. Ask me how I know this!
The "Jeep Wave" was mentioned above. Years back (35 to be exact) I owned a Jeep CJ5. Back then, mostly farmers, Forest Service personnel and other serious users owned Jeeps. They were hot in the summer, cold in the winter, and wet when it rained, so few "civilians" drove them. Then they caught on a niche vehicles, and a lot of "enthusiasts" started driving them, and along came the wave. It united folks who enjoyed going off-road, and who were willing to put up with the hot/cold/wet of a CJ.
Now we have the Wrangler, heir to the CJ. They are the "same," but different in that they are comfortable, well sealed so occupants are not cold, hot, or even wet anymore. Jeeps are now bought as an alternative to a Miata by college kids and even 40-something moms.
I own a Wrangler, and I can tell you that the "Wave" is dying as the owner group diversifies. Here in Texas, fewer Jeep owners return my Texas wave (2 or 3 fingers of the right hand raised from the steering wheel) than drivers of pick-ups. The Texas wave used to be something EVERYONE did to everyone as a sign of friendliness, at least on country 2-lane roads. There were even signs here that said "Drive Friendly." Even the general Teaxas wave is dying as people accelerate their lives, and the population diversifies.
Sprinter STARTED with this diversity, so I suspect the Sprinter Wave is a non-starter.
Bob