What's up with the prohibition on car sales in many U.S. states on Sundays?

It seems that various blue laws prevent alcohol sales in many states, but the same states tend to prohibit car sales as well. If it has to do with “machines that do work”, such as Texas’ law preventing the sale of hammers on Sundays (while selling nails is OK), why don’t those states prohibit hammer sales too? It seems that the poor cars are getting a bum rap…