Tesla just got a big boost for its newly unveiled electric tractor trailer. Walmart announced Friday that it had pre-ordered 15 of them. And it isn't the only company to do so: J.B. Hunt Transport Services also announced Friday that it had pre-ordered some electric semis, although it wouldn't say precisely how many.

At the new truck's unveiling, Tesla CEO Elon Musk said the trucks would not begin production until 2019. Given the company's incredibly bad track record at producing vehicles when it said it was going to, it could easily be a year or two after that, or maybe even more, before Walmart sees its first truck. Still, the retail giant's announcement is a really smart move.

First of all, it's great for Walmart's image. For a company best known for putting mom-and-pop stores out of business and going to extremes to stop its employees from joining unions, backing Tesla in this very public way is great publicity for Walmart. Pre-ordering the trucks is not a huge financial commitment. Reservations reportedly cost $5,000 each, so Walmart is getting all this good karma for only $75,000. Assuming Tesla's program for pre-ordering trucks works the same way as its program for pre-ordering cars, Walmart can simply cancel its order and forfeit its deposit whenever the trucks finally become available.

But it might really want to buy them. When unveiling the trucks, Musk promised that the Tesla electric semis would cost $1.26 per mile for total cost of ownership, compared with $1.51 per mile for a diesel truck. They will also run for 500 miles on a single charge. And Musk announced that the truck would have Level 4 autonomy, which means they can drive themselves in familiar settings.

Also, the Tesla trucks have a snazzy new look and the Tesla T symbol on the hood. Perhaps more importantly, the cab has been completely redesigned. Without a diesel engine on board, there's a lot more room in the cabin for the operator, and the steering wheel is in the center of the cab, rather than on the right (for most countries) or the left (for the U.K., Ireland, Japan, etc.) The design also allows the driver to stand if he or she so chooses.

And that may be the real point here. People who can drive semi trucks are in very short supply--so much so that there is an estimated shortfall of 50,000 drivers according to one estimate. The Tesla trucks will not only have self-driving features, they'll be connected electronically to a fleet management system, raising the prospect that--in a future where driverless cars are legal on the road--a platoon of Tesla trucks could travel together with perhaps only one driver in the lead truck.

But that's the future. In the present, the promise of Tesla trucks to come may be a real asset for Walmart when it comes to recruiting and retaining drivers. Who wouldn't want to work in a snazzy new Tesla truck with a roomier cab than you've ever seen before? That's probably the biggest reason Walmart's announcement is really a very smart move.