Same thing about getting laid off: it's never nice to lose your job, but even if the severance is good it's not nice to have your employer suddenly behave like an asshole, and that they think that your work is so worthless that it isn't necessary for you to wrap anything up.
Unless you have a contract with your employer around the severing of that relationship, neither parties are beholden to each other and any expectation of such behavior is ultimately unproductive and quite unhealthy (mostly for you, $bigTech doesn't care).
But layoffs can still feel like being cast out of your tribe. You lose the daily casual social interactions that humans tend to want and need, and maintaining actual friendships becomes much harder. Not to mention losing your livelihood, social status, and health insurance.
The way companies communicate to employees that they've been laid off (locked out of the building, passwords stop working, maybe an email if you're lucky, etc.) is explained well by economics and company priorities, but from the human perspective it does rub salt in the wound.
For hiring and retention purposes, companies will often claim that they treat employees well. The truth is you might be treated OK until the day you aren't, and layoff day is absolutely one of those days.
That last part is a uniquely American problem.