One could counter that example with the multitudes of businesses who failed on meeting their defined benefit pension promises, resulting in laws like ERISA 1974 and PPA 2006, which resulted in businesses ceasing to offer defined benefit pensions because turns out, predicting decades of future economic conditions and insuring volatility for that length of time is insanely costly.

Not to mention that IBM has been dying for a decade+. I certainly would not expect them to make good on any decent size DB pension in a few decades, and unless you are part of a politically connected group, you may or may not get fully bailed out by the feds (see General Motors pension renegotiations in 2008).

See also multi employer pension plans which have crazy regulations where if one employer fails, the other employers gets to pick up the tab.

https://www.americanactionforum.org/insight/the-american-res...