Why do SF billboards hit different?

i’d be super curious to hear from a software marketer why you think the ads in sf are so aimed at tech companies/workers compared to other cities - to the point it makes up a part of the culture/vibe

there’s the very obvious point that sf is a dense city with lots of tech companies, with high purchasing power, startup culture, and so on, but i can’t recall seeing even one tech ad outside of sf. even major cities like paris or london seem to have extremely few

why? is there anything to it other than the above?