I suspect one reason is that the teams granting pensions are usually long gone before it is time to pay for them. I strongly suspect that union leaders negotia

I suspect one reason is that the teams granting pensions are usually long gone before it is time to pay for them. I strongly suspect that union leaders negotiating big pensions generally do not care much for the welfare of the people they claim to negotiate for (e.g., union workers). Negotiators almost certainly know that what they ask for is unsustainable and that a more sustainable schema will be better for the workers (their benefits wound not have to be trimmed), but negotiating for bigger future payouts brings bigger career benefits and plenty of time to not be associated with this when the system finally fails.