Sure! An example would be a company website that lists the staff, and you want to have them ordered according to the importance of the role (CEO, CFO, Admin, whatever).
Telling a client to add a number to each person rather than the ability to click and drag an arrangement is not exactly ideal, for a couple of reasons. First, it’s an obvious work-around. If I’m designing a website, workarounds are fine, but it’s not great to offer work-around to clients IMO, the easier/straight forward the better. Second, if they need to add or remove a new person to the list, they would need to edit every single other entry to adjust the ordering. If you say “add a 0 at the beginning so they can do 031 and 032”, I would argue again this is an obvious work-around, and at that point is getting confusing and unorganized.