They need to be designed so that there is not a single point of failure and be interchangeable.
Senior management is usually not knowledgeable enough to successfully design teams—particularly in a fast changing world where all the challenges are not fully understood.
The best they can do if find very sharp and hard working people who can creatively fill any gaps.
Unfortunately the reverse is true. These companies have cut staffing so far that a team of four doesn't have a single point of failure if one person departs, it has four points of failure if any one of them depart.
...and the number of reasons for departing are already high enough; promotion opportunities, retirement, family issues, health decisions, etc. Adding a manager trying to force regression to less effective work in a cubicle farm can trip all four points of failure at the same time when even one would derail the entire team.