You don't gain any purchasing power when they take away pensions. They just take them away.

That's a sound functioning theory, but a terrible practical outcome. Too many people are horrible at saving money for themselves and while you can have a "screw them then" outlook on those people, the simple fact is that our society would get really screwed up after a few generations worth of millions of 80 year olds trying to work because they didn't save money and everyone else would bleed money because of it.

Then you look at the predatory business model that's in full swing where boards are literally legally required to try and make shareholders as much money as possible that are designed to try and get people to spend any money they can and it becomes even harder for many people to save. Leaving everyone to just save for themselves will simply not work in this day and age. Too many people wouldn't manage it. It would ultimately mean the government would end up dealing with the millions on penniless people, which means tax dollars would be spent on them, which means YOUD be paying for their care.

And yet everyone with pensions want to keep their pensions and everyone without pensions keep fighting to get them.