At the opening rush, staff with printed lists search for names, cross them off with a pen and try to read handwriting at the same time. The queue grows, and afterwards nobody knows exactly who came, because the crossed-off lists are hard to count and harder to type up.
Most registration tools can already put a unique QR code on every ticket or badge and export the attendee list as CSV. What is missing at many small and mid-size events is a simple way to scan those codes at the door without renting dedicated check-in hardware.