I do not understand why central banks are allowed to print money at low/close to zero interest rate. This will build up some kind of future subprime bubble wher

I do not understand why central banks are allowed to print money at low/close to zero interest rate. This will build up some kind of future subprime bubble where all the created cheap debt cannot be paid back. Central banks step in and save the financial system, more finance regulation is put in place but nothing is really solved. As an engineer working within operations, I cannot understand this as the root cause too much debt which cannot be paid back is not solved. Neither is the current economic system compatible with the environment. Common things we share like clean air and water and environment resources are not priced. You can profit from not being nice to the environment yet you do not pay for that profit.