In other words, they are there to do the job they were hired to do. Just because one volunteers to work extra hours checking people into a resort during a hurricane doesn't mean that employee is preventing loss of life.
It's Disney Inc.'s responsibility to keep its onsite guests safe at all times, not just during a hurricane. You can't leave resort guests alone on a property, so obviously employees need to be present to maintain basic hotel operations. They're "responsible to prevent loss of life" only if their job description says so. They're not the Red Cross, nor are they legitimate first responders.
If Disney can't scrape up enough employees to volunteer to work during a disaster, then you either run on a skeleton crew or management steps up to take up the slack.