It has kind of been a thorn in the side of immigration enforcement though that determining who has potentially overstayed their visa because of the lack of exit tracking. Because of that trying to enforce visa overstays was really hard because you just have a huge list of people who have come with not much info about who actually left so trying to check up on visa overstays would waste a lot of time on people who had just come and gone as required. This trims down that list to be muuuch smaller so they can more easily check without wasting a lot of time.