They also have the burden of fixing help tickets and new system enhancements in a timely fashion and any system mistakes they make can cause every link in the chain to fail, so they too have a huge burden that has to be done correctly or the entire business is hurt by it.
They take place each year because counties are fixing small tabulation errors made when adding up precinct totals on election night, as well as mistakes made in the reporting of those totals to the secretary of state's office.