The reason is that not all speakers have the same type connectors, so switching from one speaker system to another can mean changing from, say, a banana plug ( it's shaped that way ) to a solder lug ( shaped like the letter U ) or to an entirely different type connection.
22.
I / O includes three ring connectors ( plus one power one ground ) which accept crocodile clips or 4 mm banana plugs as well as a 23-pin edge connector with two or three SPI, and I�C . Health and safety concerns, as well as cost, were given as reasons for the removal of the button battery from early designs.
