They're simply doing it, because they can.
It's all very tiresome.
Remember those futuristic predictions and projections from the past; you know, where we were all going to be driving flying cars and robots were doing all the cooking and cleaning.
In reality, everyone ended up with a moggie minor and just got married.
Apart from all the obvious and not so obvious legal and technical reasons why there will never be driver-less cars on the open roads, there's one overriding reason why it will never happen.
People buy cars, to drive.
No one in their right mind is going to spend their hard earned money on a sporty BMW or fast Mercedes and then not drive it, but simply sit in the passenger seat reading the paper, as they'd have you believe.
Can you imagine the conversation with the neighbour?
Hey Dereck, I like your new car... what does it drive like?
Err... I don't know.
You may as well get one of those other things you don't have to drive, like a bus, train or get a taxi.
As for 'drones', well, where to start.
Calm down dear, it's only what we used to call a remote controlled helicopter; it's not as if it's anything new.
Well, apart from the fact that when they make an alleged 'delivery' it will just dump any package in your garden for the local riff raff to nick, I think you'll find the government will make laws regulating them so stringent, that it would be almost impossible to comply with and in effect, ban them.
Or the C.A.A. could simply us existing aviation law or safety arguments to prevent their proliferation.
Not to mention the doubtless inevitable 'security' threat; don't even go there.
Just as some thought we were going to have a sky full of cars, we're never going to have a sky full of 'drones' or roads full of driver-less cars.