Because I know myself two sets of Allstate layoffs in 2014 and 2016 where zero notice was given. The teams were literally walked to the cafeteria and informed they were being laid off, walked in groups by management and building security back to their desks to get their personals, and walked out of the building all within an hour. They wouldn't even let them pack up their desks and they sorted out and shipped them their non-Allstate affiliated belongings. They did not get severance or paid wages at all after that day. I was personal friends with many of them.
Does WARN just apply to certain numbers of people laid off? These 2014 and 2016 layoffs I witnessed did not involve nearly the numbers impacted in 2020 but each were in the couple hundreds.