*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
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