So you've got a little 900-square-foot shitshack in Santa Monica or Santa Clara or Sydney, and it cost you $1000/sf. You do the math. It sucks, but at least you've got a 6000 sf lot. What if you you wall off the lot from your house, leaving, say, a three-foot-wide space to get your front door, pave it over (or dirt it over, that'll work), and rent it out to neighbors who hitherto have had to find street parking? Imagine the coin you put in your pocket! It'd put a nice dent in your property taxes.
Well, in Japan you don't have to wish, because the dream is a reality. Houses in our neighborhood with wasteful green spaces are rare indeed; almost everyone who has more than about 50 tsubo of land has cordoned off part of it put in a parking lot, or if they've got a really big lot, like 150 tsubo, they put in a parking lot and an apartment building to go with it.