For long distance, interstate moves it's federally regulated and requires a license.
Do a quick google search on 'moving scams' and this should give you a good idea why licenses and regulations are a good idea in this industry. It's ripe for scams and shady characters.
Unbelievable, some of the stories I could tell...
Since these licenses are limited in number, yet sold freely, it's clearly a gatekeeping scheme.
State licensing varies but generally, it's easy as well.
.... go on...
Step 1: encourage people to put the vast majority of their material possessions in someone else's vehicle, and pay for the privilege to do so.
Step 2: drive away.
Car movers are also notorious for this. The fun part there is that if you don't pay the new rate, they hit the road again and it can be another week before you get your car back-- assuming it hasn't been impounded.
If you see a car carrier unloading a car or two in or near a residential area or in a corporate parking lot, it's quite likely this is part of a relocation package.
My son, then living in Washington, DC, got a job offer in California. He had little time to find an apartment, etc., and it did not seem practical to spend what time he had driving across the country. We stuffed the trunk with what it would take, drove out to Montgomery County, and handed off the car to the mover.
Buying specific cars tends to mean they're all over the country. Easier to fly there, check it out, and have it moved for you. Car collectors, for instance, though I assume the rich ones don't have these problems.
Sometimes it's cheaper to buy a car in state X and move it to you rather than buying it where you live. Also other countries, etc, though I assume you put that in the same mental-category as "over water" :)
However, some people are much to trusting and don't think to.