People get into growth mode and overhire and then have to lay off when the bill comes due. Or permanent attrition which is also stressful.
Productivity improvement via expensive tools and training is easier to pull back from when you get to the end. It slows the headcount ramp, which resides the fishtailing at the end.
Plus I just feel far better when I can say that the team can produce more functionality per month today than six months ago. Teams that slowly grind to a halt are one of my personal Hells.