Edit to include: chewing is easier to quit than smoking because you don't go out back and have a chew with your friends or go outside and take a dip to avoid someone at a party. The physical addiction to smoking is the least difficult thing to overcome.
The fact that you can chew almost anywhere makes it even harder to quit IMO. You could crank a dip at the movie theater, on the plane, playing video games on the coach, on the can, in bed, during road trips in the car with other people, in class, in church...
I worked for a lawyer here in DC who used to throw in a dip during the trial.
You don't have to take a "smoke break" or walk outside in the rain/snow/cold/heat whatever. You don't have to roll down the window and you don't force everyone around you to partake.
Goddamn it was a fantastic vice.