Consumers getting the short end of the stick

In the past, when car prices were astronomical, COEs shooting to the sky, a car buyer who bought his car on the 30th day of a month, say April, will be considered as buying the car on 1st April and his use of the car will expire on 31 March. He thus lost the use of the car by one month, due to administrative convenience. That means a lot of money. This has been rectified today and the COE will expire on the respective days when the car is registered. Today, a forumer complained in the Straits Times that banks are using 360 days as a year to compute interest rate for credit cards instead of 365 days. The net effect is that consumers will have to pay more. Another former complained that the debiting and crediting of a bank transfer of funds are not done on the same day in some banks which again is to the disadvantage of the consumers. Why are the consumers, mostly the small people, always receiving the short end of the stick? Are these ethical business practices? Big corporations should not squeeze for every little advantage they can get from the small consumers. And in the case of 360 versus 365 days, this is unacceptable as there can be no justifiable reasons for doing this.