I was driving with a friend on in Louisiana about 3am one night in the late 90s. I thought I saw something ahead in the right lane so I moved into the left lane just in case.
As we got closer there was a giant shadow of some kind with only tiny reflectors at the edges. It was a HUGE matte black boat filling the lane on a matte black trailer with no plates. Closest comparison I can come up with would be one of those river patrol boats from the Vietnam war.
We were on cruise so it took a few seconds to pass them. The boat was being towed by a matte black F-550 (?) MDT with no plates and no lights other than headlights.
I did not look up at the driver when we passed. I have no idea if this was a drug thing, an intel thing, or what.
It could be many things, but I'd guess it's just someone who thinks it's cool to have matte black everything. I had a neighbor (who was a cop) who really liked matte black vehicles. It's not like it's illegal or anything. (Although, being a cop, he very well may have been a drug dealer also, so who knows?)