Currently, order id, user id, all these id's are numbered.
This can be handy internally, but external parties can use this to check statistics:
Example: someone places an order at 00:00 day 1, and another order at 00:00 at day 2
The user can view the order id in their api request and compare the two ids:
example:
day 1 order: 35
day 2 order: 40
user knows, there were 4 orders on that day
This works with user accounts too