It's a trend in our lawmakers that make them so sensitive to being anti anything that they come up with weird circuitous laws to ban things that they don't like or have donations to eliminate.
In this case lawmakers were attempting to protect small mom and pop style dealerships from the Detroit auto industries shady business practices, but I bet they didn't want to seem "anti capitalism" for regulating the pricing of cars to ensure that the dealers weren't dumping cars to drive out the competition. So instead we get a crazy law that bans direct sales. Because its much harder to construe that as anti something, and the politicians can always fire back with a similar "anti mom and pop stores" nonsense.
For a more modern example look at abortion laws. In my great state the politicians are too afraid to go one way or the other so they come up with bullshit like waiting times. In order for a woman to get an abortion she has to wait three days. No reason. She just has to. This is because someone couldn't get an anti abortion law passed so they settled for attempting to shame the woman into keeping the child with arbitrary regulations and rules.
Same across every regulatory statute as well. We rarely ban any activity out right, but instead mire in a quicksand of impenetrable regulations and taxes.