...and that ludicrous signage you see everywhere, "Earn Vacations!", "Earn Free Flights", "Earn Free Food", none of which shows the slightest understanding of the word "earn", and I'll vary here from the dictionary to rant upon the meaning of the word earned...
It's tough. To exchange ones labour or service for cash might be an obvious example. Simple enough. We all earn our daily bread by working at things we'd probably prefer not to. So "Earn", the exchange of ones precious time or life for the necessities we need to maintain it, like food or shelter.
This is subverted or perverted in the ideology of "Earning reward miles" or "Earn free food" by the fact that you are, in fact, not earning, you are squandering money on luxuries and receiving a tiny discount to be saved and then squandered upon further luxuries. It's not "Earn", it should be entitled rather "Squander you're money here and you'll get to squander a disproportionately small amount of it here again later....".
But it's by these subtle shifts in language and ultimately thinking that they win our souls...