For anyone genuinely wondering why they don't do the implied thing and convert it to residential, the answer is that the San Francisco permitting process to build even as little as a single-family home on an unused lot can often require paying someone full-time to hassle the city government literally every single day for several years straight, and then if the NIMBYs persuade the board of supervisors against it the project gets denied anyway.
Nonetheless, commercial->residential conversions tend to be pretty popular. All those industrial-themed urban lofts in other cities sell/rent just fine
> If only there were some other high-value use for San Francisco real estate besides office space.
Converting office space to residential space is hard. Not just the zoning issues, these can be solved... the major problem is building technology. The entire HVAC system has to be ripped out and replaced, as people want individual temperature controls, to not smell whatever their neighbor is cooking or smoking and they want to have showers as well, which is problematic because office HVAC systems are not set up to deal with high humidity air and will have instant mold issues. (Side note, that is the reason why many companies, despite offering "bike to work" incentives, won't have showers installed)
Some spaces, particularly high-rises, lack windows that can be opened. A lot of space can't reasonably be rented out as many jurisdictions require a certain amount of direct sunlight for a room to be legally considered residential.
But the worst issue is plumbing: offices generally are set up with centralized loos and the kitchen nearby (if there is a kitchen at all). That keeps the amount of vertical pipes for cold, hot and waste water very low. In a residential building however, unless it's some sort of boarding house, people generally expect to have their own bathroom which means a ton of work to retrofit, more so in a way that doesn't lead to noise complaints.
It's hard to transform many office buildings into residential spaces, unless you demolish them and rebuild.
Office buildings usually have huge floorplans while residential places require windows, so any space within ~5-6meters from the wall is basically useless (bathrooms, elevator shafts, storage spacce, stairways and not much else can be positioned there)
The New York Times had a nice interactive article recently for subscribers showing how some office buildings can be and have been converted to residential. Most of the illustrations that tell the story didn’t seem to get captured by the Wayback Machine, unfortunately:
If only there were some other high-value use for San Francisco real estate besides office space.