From my perspective, management often doesn't have the information or tools to be an ally or intermediate to his or her subordinates, and trying to curate that relationship is a one-man effort, unless you have great influence at company leadership.
Some of the tools for a quid pro quo relationship that extends beyond mere money include being able to tell people about big moves so that their lives aren't caught off guard. Coworkers help each other out in this regard. But should management?
People make their plans around timing, geography, and revenue from employment, and when management doesn't reveal big layoffs, big real estate changes, or other big restructurings, people have to up-end their lives. Management knows this, but values some things more, such as the company health. In doing so they set the tone of the relationship.
Management isn't in the position to establish a rich and sincere relationship with employees. There's always an element of insincerity because management isn't telling you things that your coworker friend would, the coworker friend who calls you from another company after the layoffs, recommending you to hop ship to their company. Would management ever tell you to hop ship to Apple?
One might argue that management ought never be in a position to establish such rich and sincere relations. One gossiping manager and you might trigger an early exodus. Or a wave of salary conversation. So managers ought not even know the very information which would help their employees stabilize their life against the uncertainty.
Also, if leadership doesn't want a union, and plenty of world-class places don't like unions, what is management's position to play then? Obviously squash the union talk.