The goal there is to minimise the time spent waiting for the other shoe to drop.

After all, if you know layoffs are happening, and your boss schedules a confidential one-on-one meeting with you tomorrow, how well are you going to sleep tonight?

And what of the people who aren't getting fired - you can't really reassure them their jobs are safe before you've told the people whose jobs aren't safe. So you'll be keeping them in limbo too.

Of course, no amount of careful management is going to make people enjoy getting fired (except perhaps a generous voluntary early retirement package)