So many questions... the big one: How does Google make money from this?
Think of a conversion funnel[1]. At each step of a process toward making a purchase, you lose a certain percentage of users. Adding a payment method (typing in your credit card number, address, etc.) is tedious and requires you to have the card handy, so you lose a lot of people at this stage.
If more people are already past the hurdle of having a payment method on file, they can sell more apps/media on the Play store, more devices on the Google Store, more Drive storage upgrades, etc.
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Do they sell it? If yes, who buys these and what do the buyers do with it?
Getting your product listing to the top of Google search results is not free.