My home ISP, as most are now, have "unlimited downloads". There's no limit on usage by numbers, because consumers don't like that. Instead there's limit on usage by style. I can't run a public server on it, and I don't get a business SLA. For home usage that's ideal, I don't need those things but I don't want to worry about limits.
These plans vs API keys issues are exactly the same concept.
That argument would have been valid when the 5 hours blocks were unlimited in the beginning.