Ha! A) So the technical reason is that its their primary way of stimulating the economy. It doesn’t mean that it works, there is limited efficacy of doing thin

Ha! A) So the technical reason is that its their primary way of stimulating the economy. It doesn’t mean that it works, there is limited efficacy of doing things this particular way. B) The nontechnical reason is because they want to. Because they are buying from their buddies, or stimulating sectors of the economy that they have exposure to. And also, nobody else wants to buy low interest rate things. (But thats also part of the technical point: force people to invest in the actual economy instead of the lower yielding risk free things while the individuals pretend it was their own individual idea. But people still didnt really want to do that, although the last 2 years were the natural extreme of this, as people did do it en masse) When the central bank buys things, the person they bought from has new dollars. And that person slowly pays back those new dollars, while also using those dollars elsewhere in the economy, diluting the supply of dollars and also making sure dollars are still circulating at all. None of those three things happen perfectly. When they stop buying, they stop diluting the dollar supply. And theyre only slowly receiving new dollars back which they then delete/destroy/permanently remove from circulation. When they sell things, the same occurs: they get more dollars back at once.