Ask HN: Why are the numbers out of order at the DMV and Social Security Office?

Since moving to the USA, I have had to get a SSN and a new drivers license. Both times I went to the office, I had to get a number and wait a very long time. Duringy wait they called out the numbers out of order, ie: 125, 121, 134, 132, 127.

Really curious if anyone has any behind the scenes experience with these kinda systems?