It keeps your mouth busy with something beside food
It can help you stay awake on a long drive
It may improve concentration and cognitive performance
It tastes good.
Although most gums are very low in calories, they may contain unhealthy ingredients. Let's take a look at Wrigley's Extra Peppermint Gum, for example:
Sorbitol, Gum Base, Glycerol, Mannitol, Natural and Artificial Flavors, Less than 2% of: Hydrogenated Starch Hydrolysate, Aspartame, Acesulfame K, Soy Lecithin, BHT (to Maintain Freshness), Color (Blue 1 Lake).
Like most sugar free gums, the sweeteners used here are sugar alcohols: sorbitol, glycerol, and mannitol. All sugar alcohols end with "ol". Unlike table sugar, there is some evidence that sugar alcohols may actually improve dental health. They are slightly lower in calories when compared to table sugar, however the amount used in chewing gum makes this a moot point.
Hydrogenated Starch Hydrolysate is simply a mix of several sugar alcohols.
Despite the abundant use of sugar alcohols in this gum, the manufacturer decided to add two controversial artificial sweeteners - asparatme and acesulfame-k. Read more about their risks here.
Instead of using natural peppermint, the manufacturer chose to use Natural and Artificial Flavors, most likely a cheaper chemical option.
In order to make the chewing gum more attractive, an artificial color - Blue 1 Lake - is used. Artificial colors are banned in parts of Europe because they cause hyperactivity in some people and may be carcinogenic.
Last but not least, Butylated hydroxytoluene (BHT) is an additive used to retard rancidity. Some studies have shown it to be carcinogenic.
Luckily, there are better options out there.
Spry Sugarfree Spearmint Chewing Gum uses a very tame set of ingredients: