What makes you think the government would be qualified to issue tests? 40k+ human-caused automobile deaths per year would suggest they are pretty awful at judging human driving ability. Not to mention these companies have more rigorous internal safety tests than the government would ever be able to come up with.
What makes you think random companies should be qualified to determine whether or not their product is good enough for the public space?
The FAA does a pretty good job for aircraft some errors notwithstanding, I don't see why there couldn't be a similar institution for road vehicles. Oh, wait: https://www.ntsb.gov/Pages/home.aspx
