Because that way they can build profiles of you and use them to manipulate you into buying junk you don't need. That, in turn, makes the line go up and the share holders happy.
So that when you see all that stuff you can't afford on the neighbor/coworker or your friend's place, you can be envious, so their spending was worth it.
Same with all those car and watch ads in magazines. It's not like regular people are constantly looking to buy a new car. But the brand must be etched into brains. Your neighbor must be reasonably convinced that people around him are on the same page regarding the prestige of a certain brand, else it's not worth spending on. So even if you can't afford whatever car model, the fact that you're aware that it's prestigious is already worth it.
This is somewhat weaker in personalized online ads because your neighbor can't know what ads you saw. Billboards and super bowl ads a much better for establishing common knowledge, but perhaps that's why influencer-based marketing is gaining ground. All followers know that all followers saw the embedded ad. Maybe they should introduce ads where it says "Your friend Joe Schmo watched the following ad:"
This might hold water in 1980 when neighbors talked to each other and coworkers often worked in the same building and didn't wear Bluetooth earbuds, but I don't know so much about now.
Get with the times, grandpa. Thanks to the wonders of buy-now-pay-later services, we don't have to worry about that anymore, just stop thinking and consume!
I largely get ads for things I already have bought. Otherwise, it's really general demographic stuff that doesn't strike a chord.
I assume it's because I don't really browse for buyables unless I have the intent of buying something immediately. On a personal level, I fail entirely to understand the value proposition in web advertising.
I wonder how much of this is actual advertising working (proven by independent A/B testing) and how much of it is big tech bullshitting their shareholders and customers. Even Veritasium had a video ~10 years ago, describing Facebook's way of reducing view counts to coerce advertisers to pay higher.
That's tech capitalism in a nutshell.