Normally we chew things to make them small enough to swallow, but chewing gum doesn’t have any nutritional value. As a child I was told not to swallow it and dire warnings were added “it’ll get stuck in your appendix and you’ll land in hospital”. So it can’t be that.
Some things we chew taste good. The minty freshness of gum can be pleasant but it loses its flavour after a few minutes, so it can’t be that.
Chewing or sucking something can re-adjust the pressure in your ears on take-off or landing. Mostly we’re not on an aeroplane, so it definately can’t be that.
Next time you visit a farm, take a close look at a cow. That’s what you look like when you chew gum.
Then there’s the problem of what happens to the chewing gum after you’ve finished. Spitting it out is gross, in fact the more forceful the spit the grosser the effect. Someone in Iceland thinks it’s art. Not much to do up there I guess.