Hotel chains want you to book directly through them because it costs them less to make a reservation themselves than it does to pay a commission to Expedia or other online travel sites (or travel agents).
A dozen years ago hotel chains started to focus on driving their most frequent consumers to their websites by limiting points-earning to reservations made directly, limiting elite stay-earning, and in some cases even limiting points.
But for both a chain’s best customers and for infrequent guests, they also had to make consumers believe they’d be able to get the best deal by booking direct.
Only they don’t actually ‘promise’ the best rates. All they do is promise a process by which if a customer discovers, under certain circumstances, that they aren’t getting the best price that they might be able to have the better price matched or beaten and might be able to get some compensation as well that varies by chain.