No one has a garden either - and Japanese gardens are for observing from inside and not for playing in. That's why you find tiny parks and playgrounds through out the urban areas in Japan.
The parks and playgrounds are just dirt - which is very dusty and dirty to play on and very hard to fall on if you are learning to ride a bike. This is the Robot Park at Roppongi Hills where the architects ordered every slide from the catalogue in every colour. In winter, the air is so dry the children get a static electric shock going down the slides.
It makes you really appreciate the green grassy parks and gardens in England - especially today when the sun is shining.