Financial planning only works if the rules never change.  As a young married couple, in the 60's, we had a defined benefit plan through work.  Starting in the late 80's, due to changes and restrictions initiated by our own government, the plan benefits were  slowly chipped away.  By the 2000's, the benefits were not anywhere near what we knew it should have been at the start of our 'planning' in the 60's.

The 401k didn't appear until 1978, and very few employers offered one.  It may be better to ask why they can't invest, rather than why can't they work till death.