Whist the article hints at it, it fails to explicitly state that many managers negatively impact productivity. Companies could further improve their productivity and thus profits by eliminating excessive layers of management.

"Companies" don't make decisions, people in management positions do. These people just aren't going to fire themselves. Nor do they want to downplay in any way how super important they are by eliminating lower level management positions, because maybe that just sets them up for elimination on the next round. They will instead say more management positions are needed and critical to justify high salaries, bonuses, and other perks.

Of course it isn't completely the case - but most managers I've met in my 25+ years working are usually people that have a hard time "doing" but relatively good at "speaking". I have yet to meet a manager that's really transformed anything significant...