Some people won't be available all three days. People who work a regular weekday job won't be available on Monday. This means recruiting more workers to establish shifts for certain days and recruiting other workers for other days.
The number of workers needed is increasing. As I said in the last election, we were supposed to have 250,000 people, and we had 232,000. This led to shortages. Some polling stations opened later because of this, since workers didn't show up. That's a major challenge. In the pandemic situation, if we add the need to recruit more workers, this certainly makes things harder.