Here is how it was explained already by B1MAXX. When you see the results (not mixing with water by DOT 5 silicone base) you will see one of the bad points or reasons some say not to use it unless you change it frequently. Water not mixing with DOT 5 means the water sits in some points of the entire system where it comes in direct contact with surfaces and corrodes or rusts (steel) lines from the inside out. Not that this happens overnight but it does happen over a period of time. Just passing this on from M/C industry experience and especially ABS complicated brake systems which most classic vehicles don't have.