Earlier quoted context omitted.
Does this not happen in Europe also? It's rare for US employees to lose everything , but fairly common for pensions to be reduced to (Although I just looked, and apparently Maersk's move was specific to a UK division; perhaps this is another case where UK law sits halfway between the US and Europe? https://www.telegraph.co.uk/finance/personalfinance/2831055/... )
I don't know about other European countries, but in Netherland, it's a major cause for national alarm when a major pension fund is 10% short. This is something that happened after the mortgage crisis (because the money had been invested, and the stock market was way down), and there was a big discussion about whether people should pay extra, or pensions should be cut, or something else. It's certainly not common, and…
There are a lot of reasons for that switch: it saves on the administrative headaches of having pensions from several companies, it encourages private retirement savings (because it's "matching"), it saves companies money (because many people don't contribute), and it lets companies keep predictable finances (because it's an investment paid up front, not a lifetime or fixed-dollar obligation). But on the employee side, a lot of the reason people with bargaining power accept it is that they trust 401k funds to stay safe (except from stock market crashes), and don't trust companies to fulfill pension obligations.
The downside, as with healthcare and many other things in the US, is that when "good" jobs circumvent the problem, it takes away most of the social pressure to actually solve it for everyone.