Mass layoffs give you the opportunity to quickly purge poor performers without as much paperwork. It's advantageous to have regular rolling layoffs because of this if you can justify them by economic conditions.
There's also an effect of wanting to do smaller, pulsating layoffs over the course of many months or even years rather than one massive layoff of the size you actually need, because ultimately no one knows exactly how the machine of a corporation works, and you have to be careful not to cut so deep that you go beyond cutting out fat and start to damage critical systems.
A rapid, 90% loss of workforce like what happened at Twitter might be what the company ultimately needed, but cutting that fast and deep is an insanely risky operation that could lead to a company hobbling along in a compensatory state until it finally falls to decompensatory systems collapse that you can't recover from.
There's also an effect of wanting to do smaller, pulsating layoffs over the course of many months or even years rather than one massive layoff of the size you actually need, because ultimately no one knows exactly how the machine of a corporation works, and you have to be careful not to cut so deep that you go beyond cutting out fat and start to damage critical systems.
A rapid, 90% loss of workforce like what happened at Twitter might be what the company ultimately needed, but cutting that fast and deep is an insanely risky operation that could lead to a company hobbling along in a compensatory state until it finally falls to decompensatory systems collapse that you can't recover from.