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Why buy bonds in a no-arbitrage market?
Rates are a complex field. I will assume that context wise you are talking about rates for a individual saver quantities. The two rates you are asking about are personal bank saving account and exchange traded bonds. The points you want to compare between them are. In general, a bond is what we called a fixed rate instrument. This means that for the life of the product, it will yield a fixed percentage of its face value at a regular period. Baring any extreme circumstances (such as bankruptcy), no external factors will change the payment schedule on a bond. Conversely, by placing your money into a bank, you will accrue interest rate at some value related to some published interest rate. For example, if tomorrow, the Treasury decided to try to stimulate the economy, they could slash the interest rate, this would directly affect the rate at which your savings account would accrue interest. In general, a bond has a maturity date, where the capital is finally released from the bond. Until such date, you cannot access the money directly (you can however sell the bond, but it would likely be at a discounted value). Therefore, in general, you cannot get access to the money whenever you want it. As for a saving account, normally one can access the funds instantly, if not within a few days. This seems to the reason people seem to be focusing on. For each bond, the issuer of the bond is obligated to pay you the holder of the bond fixed payments at an interval, plus the capital at the maturity. However, obligation does not mean guarantee. If the issuer, is unable to make the payments, they may go into bankruptcy to avoid paying you. There are companies setup to advise people on the likelihood of each bond issuer on their ability to honour their debts. For example Standard and Poor issues a rating which goes all the way up to AAA for bonds. Recently, many sovereign countries have lost their AAA rating from S&P. Meaning that S&P feel that the possibility of these countries going bankrupt is non-zero. Conversely, banks may also be unable to give you your money when requested. In the US, the reserve requirements means that at any one time it only holds 10% of the money it owes to its customers. This can mean that if every customer turns up to the bank to demand their money, that bank would be unable to pay. This situation is called a Bank Run. During such a situation, the bank would likely collapse and default. In many modern countries, the government put into place guarantees on the first xxx amount in saving accounts, but otherwise, your savings could be lost. There are many complex reasons to choose one instrument over another (including some I have avoided), even if at the outset, they could appear to have the same rates.