They computerized for the same reason most things are, higher efficiency leading to lower cost. It speeds up the check-in process which means each polling locat

They computerized for the same reason most things are, higher efficiency leading to lower cost. It speeds up the check-in process which means each polling location can handle a larger number of voters reducing the cost of elections. After the fact records need to be updated to reflect which voters have actually voted. It is much faster, less labor intensive and less error prone to gather that information electronically from some iPads than pay people to review paper records and enter that information into a computer. The information is stored locally on the iPads because doing so on a server greatly increases both the potential failure scenarios and the potential attack surface of the system. Think about the impact of that server going down or a DDOS of the server. Also think about the communication infrastructure needed to and within the polling place for those iPads to reliably be able to reach the server.