Added to that: it's in the middleman's interest to blur this distinction. You can sell a lot more "may or may not be rich enough to buy your product" adverts than you can "definitely rich enough" adverts. Even if the rate per advert is slightly lower, it probably makes the middleman (Uber in this case) more money. (And the rate per advert probably won't be a lot lower because companies have fixed advertising budgets.)

So now, to justify removing someone from your pool of advertisees, they don't just need to pay what could be made by advertising to them; they need to pay for what could be made to advertise to them and (unwittingly) several poorer people.