Its very easy to make your own speaker cables yourself. One example is given here which will give you an idea.
http://www.bluejeanscable.com/store/speaker/Speaker_cable_termination.pdfBanana plugs have advantage over bare wire in instances where you are using a lower awg like 10 or 12. It can be very tough to insert the wire into the binding post with a thicker wire and in cases where the binding posts are very close together. In cases where the back portion of the electronics are tough to access due to placement, its makes it almost impossible (a real PITA anyways) to install bare wire terminated cables.