They would if they could.
https://www.ft.com/content/478fe908-5168-11ea-8841-482eed003...
Sweden raised rates recently, but only back to zero.
Swedish banks - for some reason - simply waited for the NIRP to pass and moaned.
[from the link]: Johan Torgeby, chief executive of one of Sweden’s largest banks SEB, says lenders involved in fixed income “struggled for years” and calls the end of sub-zero rates “good news”. He adds: “We have never really understood what effect negative yields have on [boosting] consumption.”
https://www.theguardian.com/money/2019/aug/13/danish-bank-la...
It certainly helps expanding the money supply. That should help increase savings, that then can be loaned out. (And simply increasing savings doesn't automatically lead to more investment: https://en.wikipedia.org/wiki/Saving_identity - I know wikipedia is not a proper source, sorry, anyway: "This identity only holds true because investment here is defined as including inventory accumulation, both deliberate and unintended. As such, this does not imply that an increase in saving must lead directly to an increase in investment. Indeed, businesses may respond to increased inventories by decreasing both output and intended investment.")
https://www.ecb.europa.eu/pub/pdf/scpwps/ecb.wp2283~2ccc0749...
"Given this finding and its robustness when tested using a variety of standard robustness checks, we conclude that NIRP has acted as an empowerment to the ECB’s asset purchase programme (APP). Banks most reliant on retail deposits have the strongest incentive to convert their EL (excess liquidity), created by the APP, into loans - and our results document that they did so."
> Personally I think it's better to err on the side of favouring whatever the "market rate" of interest would be (the rate if the central bank was taking no action to alter the supply of money or loans), and I'm very doubtful that would be negative.
Isn't the problem that the market rate would lead us to deflation?