Header wrap, just curious why not?

[sext7366]

Don't know much about this except that every time I see it advertised there is always a disclaimer which says header wraps void most header warranties.  Is this simply because it keeps so much heat it the pipes that it can literally melt the metal, or at least cause it to crack?  If so I had thought that instead of overlapping the wrap, you could spiral it down the headers without the edges touching.  Every little bit helps right?  I was just bored looking through my summit magazine and saw these wraps.  Mostly just curious why they are so bad, but also had the whacky idea that you could make the headers look like a candy cane.  I wouldn't do this though?

[firefighter3931]

The wrap can hold moisture and cause the headers to rust out prematurely. There is also a fire hazzard with the wrap because the stuff is flammable, especially if oil leaks down onto it. I consider it a "race only" modification and not recommended for extended street driving.

Ron