I'm sorry for somewhat cynical response, but... Those customers need to
believe they're getting value out of it, and it's all that counts for Facebook's business.
They target something like "people interested in computer hardware" and they get them, including those who don't need a laptop. It's bad but must be somewhat better than completely non-targeted ads, as it excludes people who have never expressed any interest (so, while having false positives at least it tries to save on false negatives). And, of course, there is opportunity for Facebook to tell how their superior ad platform is smarter than last year.
The rest (but maybe even more important than actual value advertisers are getting) is advertising of advertising - all those stories how this machine learning agile blockchain big data is our only future. And many people just believe it, and non-ironically talk how Facebook is that omniscient deus ex machina that knows us better than we do ourselves. As this meme lives, those who have a product to advertise are inclined to believe it as well (and this makes them spend money on Facebook Ads).
So, in the end, the fact you're getting ads you're not interested in is less relevant and is kind of shadowed over by the fact advertisers get somewhat better value or maybe even just believe they do.
There are shouts that the king is naked and memes that modern machine learning has two objectives: classifying data and making predictions^W^W^W^W^W bullshitting investors and raising money... but so far, such voices are in minority.