Pretty much everything is the leading cause of some kind of cancer. I had quit for about 5 years, but recently started back because not a day went by that I didn't crave it, especially when hunting, fishing, or working outdoors. I got tired of fighting the craving.
The only thing I hated was all the saliva it generated, more than the first dozen or so chews into a fresh piece of chewy.
However, I fully support an adult's choice to do so if they please.