Because they don't trust institutions, if someone that is working for a company and does something bad, or is shown to be corrupt, it will affect the public perception of the company, not of the individual.
Also, because Americans don't trust institutions, a lot of the internal processes and cultural values are upheld by the individuals, and how strongly this is done depends on the individual's power and ability to influence. This applies to all levels of the organization. This allows for the organization as a whole to be more dynamic and effective, but the downside is that this works only when the individuals have a vested interest in the organization.
When there is a layoff, or even when a simple individual is fired, this mutual alignment is removed and all bets are off. Except for fear of legal retaliation, the individual is no longer bound to the organization. This can lead to things like:
- Executives preempting the communication of their firing and using it to swing internal opinion, or even taking key team members away with them, like Sam Altman vs OpenAI.
- Employees with access to (supposedly) restricted areas copying sensitive information: E.g, sales reps getting data from all their clients to contact them and move them along.
- Plain old espionage / sabotage. Don't forget, if a company is laying people off it means they are not doing well, and if they are not doing well means they certainly want to keep as much of what is "really happening" to themselves. Fired employees can use their internal communications to gather evidence from their boss wrongdoings, find internal memos and share with journalists willing to get a scoop, etc.