This doesn't seem like a bug.
HN has autoincrementing IDs.
Reddit had a fully public API, with very little rate limiting.<p>Being a public website is not a "bug".<p>Twitter goes through lengths to stop someone from downloading all its content because Twitter <i>sells</i> that sort of access. They are motivated by financial incentives, not a desire to be 'competent' developers, or because integer IDs are some kind of amateur logic.