A very common thing people do is assume a) all corporations are evil b) all corporations never follow any laws c) any evil action you can imagine would work or be profitable if they did it.

b is mostly not true but c is especially not true. I doubt they do it because it wouldn't work; it's not high quality data.

But it would also obviously leak a lot of personal info, and that really gets you in danger. Meta and Google are able to serve you ads with your personal info /because they don't leak it/.

(Also data privacy laws forbid it anyway, because you can't use personal info for new uses not previously agreed to.)