I think you're pining for a golden age that never was. You refer to the metaphorical "pink slip." It used to be real. And it was placed in a worker's pay envelope. When the worker opened the envelope for his money, he found that note that said, in effect, "Don't bother coming back on Monday."
Sure there were good bosses in olden times who would call the worker into the office and carefully explain what was happening and why. There are still those good bosses today, but today technology, fear of workplace violence, and fear of lawsuits combine to give us new ways to be insensitive, rude and cruel.
In my years I've seen some really fascinating firings. I knew a fellow who came back from vacation to find that his office had someone else in it. His (old) boss was on vacation and unavailable, so the man had to wander down to HR to find out he'd been fired.
I witnessed a young man pulled out of a group of executives because he was wearing a green leisure suit, fired on the spot and escorted off the premises by security.
Let me climb on my soapbox for a moment. I'm the guy who trains bosses in one-on-one skills. I tell them that there's no excuse for surprise at a performance review or termination. If the boss does his or her job right, at least folks know what's coming.
Far too few companies train their people in the skills they need to talk to people who work for them about their performance. Far too many companies sanction behavior from their supervisors and managers that they would recoil from if their children did it.
There is simply no excuse for not treating people like people. There may never have been a golden age of business courtesy, but there's no reason why we can't create one.