That's really the problem, at least here in SF. The tech industry needs highly skilled employees, rather than local residents. So wherever they land, they bring in a bunch of new people who also need housing (and have high incomes.) I don't think that's inherently bad - but if your city has a bounded housing supply like SF, it's inevitably going to lead to rising rents and displacement of existing lower income residents.

(Contrast that with say, auto manufacturers, who would maybe bring in some managers when opening a plant but would also employ tens of thousands of locals, raising the incomes of the existing resident more than bringing in new transplants.)