Do you realize how dangerous automobiles are? You're piloting several thousand pounds of steel around a populated area at high speed.
No one argues this is not true, it's the premise that's unlikely.
Can you offer more details?
Realize here that we're not talking about software running on a server in a nice temperature controlled room. This is software controlling hardware that is under constant vibration, will get sticky, or bend, or break, or ice up under variable conditions - hot, dry, rainy, wind gusts as it goes from behind a building to crossing an intersection. There is a mind boggling number of things that can go wrong when you're controlling a device in the 'real world.'
Even if the software is perfect there is still a large number of variables to account for and most of them can't be controlled. There's a case for UAVs and I would love to get involved with them, but building a reliable UAV and properly maintaining it would almost certainly cost too much to have it deliver tacos. Unless you're willing to spend $250 to avoid walking a few blocks.
Should we start testing UAVs for commercial applications? Yes. Should we allow 13 years old kids to code on them and build their new cool pizza delivery service? Not yet, I think. Just my $0.02.
At the moment, a 13 yr old could fly a radio controlled F-15 legally, so long as it was for recreation and not for commercial usage.
I'm talking, of course, of the 'killer' app - assassination!