Advertisers target the people likely to see the ad and spend money on the topic. Billboards are extremely geographically restricted, so local interest dominates. This isn't really news.
And yes, they are annoying.
They must work, because they're buying the ad space for about three relevant people.
But there aren't very many blue collar tech jobs beyond security and the cafeterias. It undoubtedly feels like an invasive species for much of the lower middle class, who's been here longer than the tech workers.
Have you ever driven through farm country? I do fairly regularly (on an interstate). There's like one billboard for a (cattle) vet on my route. Most ads are for restaurants, healthcare, and the regular stuff.
And if that is the argument, there are plenty of local business billboards in the Bay Area as well.
I don't have an argument, it's just what you describe doesn't match my experience.