alt Hacker News*edit: sorry, misread that. My answer is not valid to your question.
original answer: because if you dont come up with these ints randomly they are sequential which can cause many unwanted situations where people can guess valid IDs and deduce things from that data. See https://en.wikipedia.org/wiki/German_tank_problem
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javaunsafe2019 • last Monday at 11:22 AM
So We make things hard in the backend because of leaky abstractions? Doesn't make sense imo.
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Hence the presumed implication behind the public_id field in GP's comment: anywhere identifiers are exposed, you use the public_id field, thereby preventing ID guessing while still retaining the benefits of ordered IDs where internal lookups are concerned.
Edit: just saw your edit, sounds like we're on the same page!