Giving birth ye olde style

So, in the books and TV shows and movies about women going into labour, the things that always seem to happen are that the father is never around (smoking a cigar somewhere else entirely or worriedly pacing in another room), water is boiled, and sheets are frantically torn into strips.  I get that labour was seen as secret women's business and that sometimes the father would be more hindrance and help, and I get that the water is for sterilising things, but what on earth is the sheet tearing for?!  Anyone?