You do that because its not an either/or decision, and the bidding nature of digital advertising means the lower effectiveness will be reflected in what you're paying. You can be paying a premium for people searching to buy gardening gloves, a little bit for people reading gardening stuff, and then a pittance for people that may be related to gardening in some fashion.

You're extrapolating based on your own actions rather than measuring the result. The results say that if you show gardening gloves to enough people at random, you'll eventually get some sales. Everything else is just narrowing down "random" a little bit.

Because it does add value.

Brand awareness/clout. A reminder that you need or want that thing.

You can do that kind of advertising without collecting this much data and creating psychological profiles on every user (think: Coca-Cola).

And even if I like something seeing it repeatedly online just annoys me more than it inspires me to buy their stuff. I think they'd get more bang for their buck by having social media personalities that align with their target market push their product (think: Nike).

If people are likely to be consumers of those things then they'll probably digest media related to those things or other media in the same demographic. This is classic marketing and it doesn't require the level of privacy abuse that Facebook has been trying to justify.

Agreed.