It’s already bad enough in Boston, particularly as you get closer to the airport, but San Francisco is absolutely plastered with ads for slop machines and related corporate nonsense. Maybe if you live there it’s so dull that your brain stops seeing it—almost becoming a weird kind of ad blocker. But if you’re just visiting for a few days it’s obvious, and it’s in your face all the time. It’s gross and annoying and it makes you miss random ads for medications you’ll never need (I’m exaggerating of course—pharma ads are also annoying and they should not exist).
tl;dr:
And the message is this: if you do not understand these billboards, this city is not for you.