They are actually used because a fuse is rated at a max amperage draw before blowing to protect the circuit. A fusible link is designed to protect the circuit but allow a greater momentary draw such as cranking circuits. In some cases you would be replacing fuses all the time, however the fusible link is a little more forgiving while still doing its job.I don't know either, they are a pain as far as I'm concerned. The location is right next to the starter so maybe they were put there to keep from using too much room that a fuse would take up. Doesn't matter they are getting the treatment!