They fill an important gap although I personally believe that electric bikes are a far better match particularly for the 16 year old kids who drive those things around.
Basically I'd feel much safer driving in the UK if Prince Philip was behind the wheel of one of these instead of the mobile tank that he drives ;)
I'm really surprised the Japanese mini-trucks havn't taken off in the USA. They would be great for busy city streets where parking and space could be problematic. They also don't cost very much (used 5k USD).
There was a small boom for importing them to use as farm trucks, but you can't import them until they are 25 years old if you want to drive them on the road. Most other countries have less restrictive import requirements, so they tend to go to those countries first. Not many left by the time they get to 25 years old.
It's certainly better crash protection than a pedestrian, a bicycle, a moped, or a Segway which seems to be the competition.
Regardless, a bicycle moving at 25mph being hit head on by a car moving 25mph is going to be (at best) comparable to this thing getting hit at 25mph.