Most people can't afford a single family home close to the city, so they're building for product-market fit. If you want a single family home, there are plenty in Tracy and Gilroy.
3 story townhouses were so 2018. It’s all about 4 story townhouses now.
City governments do not want single family homes but only multi storeyed houses on small lots. They prefer high density communities as that means less money required for providing utilities and services.
Single family house are the main cause of suburban sprawl and terrible traffic. Building denser is good for the Bay Area.
Townhomes are awesome if you love HOAs, shared land, shared walls, and nonexistent property lots.
Nothing unusual. It's a natural state in evolution.
Grab the SFH while you can.
If you buy a lot for 2M with the intent of developing and selling homes, would you build 10 1M townhomes or 1 2.5M SFH? The market won’t tolerate 1 10M SFH.
Bygone not forgone.
Land costs money. It’s cheaper to build up.