You do 1 because it's cheap and because it generates results.
If I search for "carpet cleaning in san francisco" on google I see 3 ads. I suspect that those ads are responsible for a fair amount of business to those companies, explaining why they pay google for the advertising.
The difference between ads on google and ads on a social network is that ads that are relevant to your search are actually often desired and far more likely to be used. If I'm searching for a carpet cleaner in san francisco then ads of such kind are useful to me. In contrast, ads embedded in social networking sites are distractions from the activities people engage on there. If some carpet cleaning company pushes an ad on me because they've discovered I live in the area and/or have pets I will more likely than not think "ugh, who are these assholes?" or perhaps "maybe I should install ad block". When I actually need a carpet cleaner I'm not likely to think "hey, I should use that company that keeps annoying the crap out of me on facebook", instead I'm likely to go to google, search, compare some reviews, and pick a company that seems decent and inexpensive.
If I search for "carpet cleaning in san francisco" on google I see 3 ads. I suspect that those ads are responsible for a fair amount of business to those companies, explaining why they pay google for the advertising.
The difference between ads on google and ads on a social network is that ads that are relevant to your search are actually often desired and far more likely to be used. If I'm searching for a carpet cleaner in san francisco then ads of such kind are useful to me. In contrast, ads embedded in social networking sites are distractions from the activities people engage on there. If some carpet cleaning company pushes an ad on me because they've discovered I live in the area and/or have pets I will more likely than not think "ugh, who are these assholes?" or perhaps "maybe I should install ad block". When I actually need a carpet cleaner I'm not likely to think "hey, I should use that company that keeps annoying the crap out of me on facebook", instead I'm likely to go to google, search, compare some reviews, and pick a company that seems decent and inexpensive.