They want to pay less interest for the national debt. Since it went below 3% people who retired have had to kill their principle and go on welfare which makes more national debt. It’s a lose lose situation.
This is only part of the problem.
The next Big Bang will be in Retirement funds that are not able to achieve anywhere close to the returns they need to meet their obligations due to this interest rate suppression
What this means is some time in the very near future the shortfall will have to be made up. In the case of defined benefit plans, today found mostly in the government sector, taxes will have to be raised to cover them.
This is very deflationary for the economy.