Infill housing is one possible solution to urban sprawl. Also, as land becomes more expensive, lot sizes shrink. As construction of single family homes ceases to be profitable, builders and developers are less likely to risk investing in them. Many inner cities change the zoning laws to reflect this. Neighborhoods originally zoned for single family homes get upgraded or downgraded depending on your perspective, to townhomes and rowhouses. People adapt to these changes or they move to the suburbs where lot sizes and zoning laws reflect what they were used to. But, even the suburbs are changing with two and three story houses on smaller lots.
The neighborhood I live in was developed in the mid to late 70's. Lot sizes vary from 8 to 12 thousand square ft. The property my house sits on is just under 10,000 sq. ft. My previous home was in a neighborhood developed in the 50's and 60's. The house was a little greater than half the size of this place and it sat on a 13,000 sq. ft. lot as did the other houses in that neighborhood.
My parent's home in Encino, CA was built in the late 40's on slightly less than an acre lot, which is three times as deep as it is wide. Today, it is one of only a couple of houses where these deep lots weren't sub-divided with a flag lot in the back. My wife's childhood home has over 11,000 sq. ft. of living space and still sits on a half acre lot in Beverly Hills, CA just north of Sunset Blvd. Many of these big old houses have been torn down and rebuilt because the land is so valuable. In this case rather than the lots being subdivided the houses have become even larger then the previous ones.
Real Estate is ever changing. Sometimes zoning laws sometimes are adapted to reflect today's needs and other times not so much. Historic Eastmoreland, a neighborhood in Portland with big old houses which are sometimes built on double lots has been the source of controversy and neighborhood rebellion against new zoning laws that make it profitable to tear down these mansions and build two or three Mc Mansions on the land.
