seems OP is not talking about compensation of the deal itself but rather compensation for the actual flight rather than a $100 voucher. Assuming his flight to Brazil was much more than that
Why should the entire flight be compensated? The airline provided the flight, just 24 hours later (and the delay is what the $100 are supposed to compensate).
Because the customer purchased a flight on a specific date, which was not delivered.
If you book a hotel room for 1-7 August to visit a conference, would you be okay if they said "oopsie, it'll be available for you 10-17 August, here's a $100 compensation"? What about a rental car, or food delivery? Is it okay for your wedding photographer to show up a day late? Of course not, the product you bought is inherently time-sensitive.
Many businesses have a notion of partial delivery. If you hire a contractor to build an extension on your house and they get sick halfway through the project and hand off to another contractor who completes it a few weeks or even months late, you don't get it for free.
