Take Twitter, which recently moved into new headquarters in a long-vacant high-rise on Market Street in one of San Francisco’s poorest neighborhoods. The company’s decision to stay and expand in San Francisco was controversial (Twitter received considerable — and highly controversial — tax incentives from the city and overwhelming support from Mayor Ed Lee), and it was expected that the company’s presence in a depressed section of a major thoroughfare would help revitalize it.

A walk though that neighborhood reveals that this has yet to happen. Twitter employees are fed breakfast, lunch, dinner and snacks on site. (Their in-house dining area is, of course, called “The Commons.”) As such, they have little incentive to leave the building. This would seem to be a perk, but think about it: mealtime was once a break from work, now it’s just an extension of the workday. The building has no ground floor retail (apart from a pre-existing Walgreen’s) — though plans for a market and at least two upscale restaurants are underway. Potential new proprietors of, say, a new cafe, pizza place or boutique are kept away by the area’s now skyrocketing commercial rents — though many buildings remain vacant as landlords hold out for the highest bidder. Even if they could afford the rent, small businesses also understandably fear opening a business where pedestrian activity seems limited to the beginning and end of the workday.

What is emerging in the neighborhood is a strong uptick in evictions — there was an increase of 38.2 percent in 2013 from 2012. (Per their community benefits agreement with the city, Twitter has been donating a nominal number of legal assistance to some neighboring residents facing eviction.) This city may be the fulcrum of innovation, but little of its disruptive thinking is doing anything to address that urban reality.

Indeed, the physical manifestation of the “public square” — another favorite civic concept embraced by the tech sector, up there with “town hall” — alas is most visible in the large numbers protesting the city’s record-breaking number of evictions.

In “The Death and Life of Great American Cities,” Jane Jacobs wrote, “Cities have the capability of providing something for everybody, only because, and only when, they are created by everybody.” We’re losing that here. The further the tech sector gets from the reality of the problems it’s engaging with, the smaller piece of the problem they’ll end up actually fixing.