Multiple reasons.
1. People have lost family members, and if WDW vacations are closely associated with departed family members, it may only be a reminder which causes pain. Although some might be able to feel comfort remembering all of the happiness. We all grieve differently.
2. People may not want to visit until they no longer have to wear masks, social distance, etc. Others may feel that they want to avoid crowds a little longer.
3. Many people have lost jobs and businesses, and every penny is needed to get back on their feet.
4. Many people might just be concerned about the future - for a variety of reasons - so just want to hunker down at home and save resources. Especially if they are concerned about natural disasters (hurricanes, earthquakes, floods, forest fires, etc) in addition to Covid-19 second wave, along with social/political issues - but those can be discussed on the correct forum, which isn't this one.