Chewing gum (as in, a chewy substance you chew for the sake of chewing) was discovered/invented a long time ago, probably before money. It was a naturally-occurring part of the tree. If you mean modern chewing gum, it had to differentiate itself from the previous iteration of chewing gum.
This reminds me of a comedy sketch I heard once which was someone returning from the new world in the 1500's and was pitching the idea of smoking to an investor.
"But why would you do that?"
I found the sketch very funny at the time, but have since found out that the real initial pitch answer was "It cures everything!".
"Anything that harms a man inwardly from his girdle upward might be removed by a moderate use of the herb."