So they can very easily be moved around like a hot dog cart.
This is the first one Elvis built for a 60yr old woman. 
Says he spent $500 plus donated materials from building supply companies.
You must be thinking of one of these push carts with swivel front wheels and large diameter rear wheels. Add the umbrella and signs and it's the old style NYC Dirty Dog stand.
If you've ever seen one being moved on the street then you know that the men have to lean heavily to move the cart and can barely move them up a very slight grade. Not to mention trying to stop one. The newer gourmet style is double and triple this size and are on trailers, as in need a truck to be moved.
Now imagine an unhealthy 60 year old woman trying to move this behomoth with it's hand truck castors through an intersection without being able to see in front of it or around it.
This is a bleeding hearts feel-good project with many unintended consequences, most of them unpleasant.
Elvis is also ignorant of basic construction techniques and materials. Probably only has an electric saw and drill.
And if his main concern was the poor woman freezing to death, in Los Angeles!.... maybe he should have thought to includes some insulation behind the flake board.
I'll leave it to others to figure out the dangers from other derelicts and bad guys....