Watch some of those older movies and you might see someone take out a cigar and bite the tip off before lighting it. Although it adds drama to the scene (especially in war movies), biting off the tip of a cigar is not recommended. It's one of those things that no one should try at home because although you may or may not damage your teeth, there's a very good chance that you will cause harm to the cigar. When you ravage a cigar with your teeth, the tip is removed with a ripping action that leaves a jagged edge.
No doubt, some people reading this might be thinking, "So what? That's not going to affect the experience or taste". However, veteran aficionados wouldn't dream of lighting up any cigar without using some type of official cigar cutter. They insist on using a cigar cutter for prepping that CAO Brazilia or Gispert because they know that it improves the experience. A quick clean chop off the tip of a cigar results in a better draw and more even smoke than using teeth to chew away at the tip. Running the risk of a diminished cigar smoking experience is never worth it so true aficionados always use a quality cutter.