Equally those same people have paid taxes for 40 years, paid into social security (to the benefit of their elders) and so on.

Keeping them in the work-force is largely undesirable. A job occupied by a 70 year old is a job not occupied by someone younger. If retirement age was say 80 instead of 60, there would be 25% fewer jobs to go around. (using imprecise simple math).

Look, most all of us will get old and eventually claim on social security or whatever. Politically just "ending that" is pretty much a non-starter to anyone who has been contributing for any length of time. Even fiddling with the edges of it (raising the retirement age) will get you voted out of office.