Prices convey information. Price controls have unwanted effects, and for that reason, for the most part, are no longer used, in the US at least. Well the interest rate is a price. It coveys information between consumers and producers. When interest rates are low producers tend to invest in high order production, longer term investments, things like capital goods. It is a good time for them to do this, because money is relatively cheap. If the interest rate is untampered with, consumers will be consuming less at this time, because they wish to keep their money in the bank, which is why interest rates are low; the banks have more money to loan, which means that consumers will spend that money later, on the goods which producers are investing in now, but are not yet ready for consumption. When interest rates are high, it is because consumers are spending money now, and are not keeping it in the bank, which is why interest rates are low; banks have less money to lend, and producers only need to be worrying about production, which is what they will tend to do at this point, given the high price of money.
When large amounts of money are added to the market whenever the government thinks it needs to stimulate or when banks just think they can issue more debt (without a central bank they can do so in unison as long as courts allow it), interest rates can no longer convey the correct information and a mismatch occurs between consumers and producers. At this point many sectors are on an unsustainable trajectory and resources are being wasted. Many projects are being undertaken for which the resources needed for their completion do not exist. At some point in the future, a correction will need to take place, at which point, if there is a central bank it will likely inject money into the market, preventing the needed correction which means the economy is still on an unsustainable course and a correction is still coming. The tendency for the market to correct at any given time will become greater. The frequency of injections, and amount of money required to stimulate the economy will increase. At some point something has to give.